Physics Questions and Answers September 14, 2022

Find the total pressure experienced by a diver 8 meters below the sea surface.

The figure below shows an electric heater placed midway between flask A and B. flask A is shinny on the outside and flask B is blackened on the outside. a) Name the process by which heat travels from heater to the flask. b) State the observation that will be made.

03 Shinny flash A X B LY HEATER reeeee Y 11 1 blackened Flask Liquid.

You are provided with the following; -A stopwatch -Cotton thread at least 120cm long -Stand and a clamp -Pendulum bob -Metre rule Arrange your apparatus as shown Proceed as follows; i)Adjust the length Lof the pendulum to 1meter. ii)Displace the bob side ways to an angle of about 45o (estimate) and let the pendulum switching for 10 oscillations

You are provided with the following apparatus. a Convex lens A candle White screen Lens holder Metre rule Set up the apparatus as shown in the figure below. Place a lighted candle at object distance, U = 20cm. Move the screen, towards or away the lens until a sharp image of the candle flame is obtained on the screen. Measure the distance V and

Candle U Convex lens White Screen

A) The coils P and S are connected as shown below. P is connected to a battery, rheostat and a switch K . S is connected to a galvanometer G II) When K is opened. b) A transformer has 200 turns in the primary coil and 1000 turns in the secondary coil. If the transformer is 100% efficient and the current in the secondary coil is 0.15A, determine

So now K tilla G State the behaviour of the pointer on G in the following cases 1) When K is switched on (closed)

Figure below...shows a battery of e.m.f 3.0v connected in series will two capacitors. S 3.0 V H 3.0F 3.0F Determine the energy stored in the combined capacitors when the switch is closed.

A piece of wire of crosssectional area 2 mm has a resistance of 300 2. Find (a) the resistance of a wire of the same length and material if the crosssectional area is 5 mm. (b) the crosssectional area of a wire of the same length and material of resistance 75022

Calculate the resistance of a 2 km length of aluminium overhead power cable if the crosssectional area of the cable is 100 mm. Take the resistivity of aluminium to be 0.03 x 10 m.

Determine the resistance of 1200 m of copper cable having a diameter of 12 mm if the resistivity of copper is 1.7 x 1082m.

The resistance of a coil of aluminium wire at 18C is 2002. The temperature of the wire is increased and the resistance rises to 240 2. If the temperature coefficient of resistance of aluminium is 0.0039C at 18C, determine the temperature to which the coil has risen.

A mass of 1000kg is raised through a height of 10 m in 20s. What is (a) the work done and (b) the power developed

A portable machine requires a force of 200N to move it. How much work is done if the machine is moved 20 m and what average power is utilized if the movement takes 25 s

An electric heater consumes 1.8 MJ when connected to a 250 V supply for 30 minutes. Find the power rating of the heater and the current taken from the supply.

Determine the p.d. which must be applied to a 2 k2 resistor in order that a current of 10mA may flow.

What is the resistance of a coil which draws a current of (a) 50 mA and (b) 200 A from a 120 V supply

Calculate the power dissipated when a current of 4 mA flows through a resistance of 5 km2.

A 12 V battery is connected across a load having a resistance of 40 2. Determine the current flowing in the load, the power consumed and the energy dissipated in 2 minutes.

Electrical equipment in an office takes a current of 13 A from a 240 V supply. Estimate the cost per week of electricity if the equipment is used for 30 hours each week and 1 kWh of energy costs 13.56p.

Determine the power dissipated by the element of an electric fire of resistance 202 when a current of 10 A flows through it. If the fire is on for 6 hours determine the energy used and the cost if 1 unit of electricity costs 13 p.

Problem 20. If 5 A, 10A and 13 A fuses are available, state which is most appropriate for the following appliances, which are both connected to a 240 V supply (a) electric toaster having a power rating of 1 kW (b) electric fire having a power rating of 3 kW.

Which are the two types of physical quantities? Explain

Tube A has both ends open, while Tube B has one end closed, otherwise they are identical. What is the ratio of fundamental frequency of tubes A&B?

In an experiment of simple pendulum , a student made several observations for the period of oscillations. His readings turns out to be 2.63s,2.56s,2.42s,2.71s and 2.80s. Find Mean period of oscillation. Absolute error in each reading. Mean absolute error. Fractional error Percentage error

A ) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion. B ) If both Assertion and Reason are correct but Reason is not the correct explanation of Assertion. C ) If Assertion is true but Reason is false. D ) If Assertion is false but Reason is true.

When percentage errors in the measurement of mass and velocity are 1 and 2 respectively, the percentage error in KE is 5. Reason KE or E 1mv, AF Am m 2 V

The wavelength of the carrier waves in a modern optical fibre communication network is close to: (a) 600 nm (b) 2400 nm (c) 1500 nm (d) 900 nm

In an LR-C network, the capacitance is 10.61 nF, the bandwidth is 500 Hz and the resonant frequency is 150 kHz. Determine for the circuit (a) the Q-factor, (b) the dynamic resistance and (c) the magnitude of the impedance when the supply frequency is 0.4% greater than the tuned frequency.

In an LRC network, the capacitance is 10.61 nF, the bandwidth is 500 Hz and the resonant frequency is 150 kHz. Determine for the circuit (a) the Qfactor, (b) the dynamic resistance and (c) the magnitude of the impedance when the supply frequency is 0.4 greater than the tuned frequency.

Determine for the parallel network shown in Figure 32.11 the values of inductance L for which the network is resonant at a frequency of 1 kHz.

Determine for the parallel network shown in Figure 32.11 the values of inductance L for which the network is resonant at a frequency of 1 kHz Figure 32.11 452 1002 302

A coil of inductance 351.8mH and resistance 8.84 2 is connected in series with a 20 F capacitor. Determine (a) the resonant frequency, (b) the Q-factor at resonance, (c) the bandwidth and (d) the lower and upper -3 dB frequencies.

A coil of inductance 351.8mH and resistance 8.84 2 is connected in series with a 20 F capacitor. Determine (a) the resonant frequency, (b) the Qfactor at resonance, (c) the bandwidth and (d) the lower and upper 3 dB frequencies.

A series R-L-C circuit is connected to a 0.2 V supply and the current is at its maximum value of 4 mA when the supply frequency is adjusted to 3 kHz. The Q-factor of the circuit under these conditions is 100. Determine the value of (a) the circuit resistance, (b) the rirenit inductance, (c) the circuit capacitance

A series RLC circuit is connected to a 0.2 V supply and the current is at its maximum value of 4 mA when the supply frequency is adjusted to 3 kHz. The Qfactor of the circuit under these conditions is 100. Determine the value of (a) the circuit resistance, (b) the rirenit inductance, (c) the circuit capacitance

A filter in the form of a series L-R-C circuit is designed to operate at a resonant frequency of 20 kHz. Included within the filter is a 20mH inductance and 8 2 resistance. Determine the bandwidth of the filter.

A filter in the form of a series LRC circuit is designed to operate at a resonant frequency of 20 kHz. Included within the filter is a 20mH inductance and 8 2 resistance. Determine the bandwidth of the filter.

An R-L-C series circuit is comprised of a coil of inductance 10mH and resistance 82 and a variable capacitor C. The supply frequency is 1 kHz. Determine the value of capacitor C for series resonance.

An RLC series circuit is comprised of a coil of inductance 10mH and resistance 82 and a variable capacitor C. The supply frequency is 1 kHz. Determine the value of capacitor C for series resonance.

A coil having a resistance of 102 and an inductance of 75 mH is connected in series with a 40F capacitor across a 200 V a.c. supply. Determine (a) at what frequency resonance occurs, and (b) the current flowing at resonance.

A coil having a resistance of 102 and an inductance of 75 mH is connected in series with a 40F capacitor across a 200 V a.c. supply. Determine (a) at what frequency resonance occurs, and (b) the current flowing at resonance.

A Schering bridge network is as shown in Figure 30.7. page 466. Given C=0.2 F, R 2002, R3=6002, C3=4000 pF and the supply frequency is 1.5 kHz, determine, when the bridge is balanced, (a) the value of resistance Rx, (b) the value of capacitance C. (c) the phase angle of the unknown arm, (d) the power factor of the unknown arm and (e) its loss

A Schering bridge network is as shown in Figure 30.7. page 466. Given C0.2 F, R 2002, R36002, C34000 pF and the supply frequency is 1.5 kHz, determine, when the bridge is balanced, (a) the value of resistance Rx, (b) the value of capacitance C. (c) the phase angle of the unknown arm, (d) the power factor of the unknown arm and (e) its loss angle.

An a.c. network consists of a coil, of inductance 79.58 mH and resistance 1822, in parallel with a capacitor of capacitance 64.96 F. If the supply voltage is 2500 V at 50 Hz, determine (a) the total equivalent circuit impedance, (b) the supply current, (c) the circuit phase angle, (d) the current in the coil and (e) the current in the capacitor.

For the Wien bridge shown in Figure 30.9, R R330k2, R1k22 and CC31nF. Determine, when the bridge is balanced, (a) the value of resistance R, and (b) the frequency of the bridge.

A 3022 nonreactive resistor is connected in series with a coil of inductance 100mH and negligible resistance. The combined circuit is connected to a 300 V, 50 Hz supply. Calculate (a) the reactance of the coil, (b) the impedance of the circuit, (c) the current in the circuit, (d) the power factor of the circuit, (e) the power absorbed by the

A 300 kVA transformer is at full load with an overall power factor of 0.70 lagging. The power factor is improved by adding capacitors in parallel with the transformer until the overall power factor becomes 0.90 lagging. Determine the rating (in kilovars) of the capacitors required.

The circuit shown in Figure 29.9 dissipates an active power of 400 W and has a power factor of 0.766 lagging. Determine (a) the apparent power, (b) the reactive power, (c) the value and phase of current and (d) the value of impedance Z. 10030 V Figure 29,9 402 Z

The admittance of a circuit is (0.04010.025) S. Determine the values of the resistance and the capacitive reactance of the circuit if they are connected (a) in parallel, (b) in series. Draw the phasor diagram for each of the circuits.

Determine expressions for the impedance of the following admittances (b) (0.001 j0.002)S, S. (a) 0.00430S, (c) (0.05j0.08)

For the circuit shown in Figure 27.17, determine the values of voltages V and V if the supply frequency is 4 kHz. Determine also the value of the supply voltage V and the circuit phase angle. Draw the phasor diagram. 1620A Figure 27.17 V 80 72 512 1 I 2.653 Fi 1 72 1 1 I I ( 0.477 mH I

Determine the value of impedance if a current of (7j16) A flows in a circuit when the supply voltage is (120j200)V. If the frequency of the supply is 5 MHz, determine the value of the components forming the series circuit.

A 200 V, 50 Hz supply is connected across a coil of negligible resistance and inductance 0.15 H connected in series with a 32 52 resistor. Determine (a) the impedance of the circuit, (b) the current and circuit phase angle, (c) the p.d. across the 3252 resistor and (d) the p.d. across the coil.

The impedance of an electrical circuit is (30j50) ohms. Determine (a) the resistance, (b) the capacitance, (c) the modulus of the impedance and (d) the current flowing and its phase angle, when the circuit is connected to a 240 V, 50 Hz supply.

Determine, in polar and rectangular forms, the current flowing in an inductor of negligible resistance and inductance 159.2mH when it is connected to a 250 V, 50 Hz supply.

Determine, in polar and rectangular forms, the current flowing in an inductor of negligible resistance and inductance 159.2mH when it is connected to a 250 V, 50 Hz supply.

Determine the values of the resistance and the seriesconnected inductance or capacitance for each of the following impedances (a) (12j5)2, (b)j4052, (c) 30260 2, (d) 2.20 x 10630 2. Assume for each a frequency of 50 Hz.

Determine the two square roots of the complex number (12 j5) in Cartesian and polar form, correct to three significant figures. Show the roots on an Argand diagram.

Two impedances in an electrical network are given by Z =4.7/35 and Z 7.32-48%. Determine in polar form the total impedance Zr given that Zr=Z Z/(Z + Z)

An equation derived from an a.c. bridge network is given by 1 R R3 (R jL2) (VR) joC R, R3, R and C are known values. Determine expressions for R and L in terms of the known components.

For the induction motor in Problems 10 and 11, if the stator losses are 650 W, determine (a) the power input at full load, (b) the efficiency of the motor at full load and (c) the current taken from the supply at full load, if the motor runs at a power factor of 0.87 lagging.

Determine for the induction motor in Problem 10 at full load, (a) the rotor current, (b) the rotor copper loss and (c) the starting current.

A threephase induction motor is supplied from a 50 Hz supply and runs at 1200 revmin when the slip is 4. Determine the synchronous speed.

A threephase, 60 Hz induction motor has two poles. If the slip is 2 at a certain load, determine (a) the synchronous speed, (b) the speed of the rotor and (c) the frequency of the induced e.m.f.s in the rotor.

A threephase twopole motor is to have a synchronous speed of 6000 revmin. Calculate the frequency of the supply voltage.

A stator winding supplied from a threephase 60 Hz system is required to produce a magnetic flux rotating at 900 revmin. Determine the number of poles.

A series motor runs at 800 revmin when the voltage is 400 V and the current is 25 A. The armature resistance is 0.452 and the series field resistance is 0.2 12. Determine the resistance to be connected in series to reduce the speed to 600 revmin with the same current.

On fullload a 300 V series motor takes 90 A and runs at 15 revs. The armature resistance is 0.152 and the series winding resistance is 50 m2. Determine the speed when developing full load torque but with a 0.252 diverter in parallel with the field winding. (Assume that the flux is proportional to the field current.)

A 500 V shunt motor runs at its normal speed of 10 revs when the armature current is 120 A. The armature resistance is 0.252. (a) Determine the speed when the current is 60 A and a resistance of 0.522 is connected in series with the armature, the shunt field remaining constant. (b) Determine the speed when the current is 60 A and the shunt field

A d.c. series motor drives a load at 30 revs and takes a current of 10 A when the supply voltage is 400 V. If the total resistance of the motor is 252 and the iron, friction and windage losses amount to 300 W, determine the efficiency of the motor.

A 250 V series motor draws a current of 40 A. The armature resistance is 0.15 2 and the field resistance is 0.05 22. Determine the maximum efficiency of the motor.

A 320 V shunt motor takes a total current of 80 A and runs at 1000 revmin. If the iron, friction and windage losses amount to 1.5 kW, the shunt field resistance is 40 52 and the armature resistance is 0.2 2, determine the overall efficiency of the motor.

One can measure the speed v of a bullet by using a ballistic pendulum. Let the mass of the bullet m8g. The mass of the wooden pendulum is M8 kg. The bullet is shot, and the system made of Wood Bullet starts swinging with the initial velocity V upward, as much as h5 cm. a) (10 p) Via using the law of energy conservation and the law of linear

A 3 F capacitor is connected to a supply of frequency 1 kHz and a current of 2.83290 A flows. Determine the value of the supply p.d.

A 240 V shunt motor takes a total current of 30 A. If the field winding resistance R 150 22 and the armature resistance R 0.422, determine (a) the current in the armature, and (b) the back e.m.f.

A 200 V d.c. shuntwound motor has an armature resistance of 0.4 22 and at a certain load has an armature current of 30 A and runs at 1350 revmin. If the load on the shaft of the motor is increased so that the armature current increases to 45 A, determine the speed of the motor, assuming the flux remains constant.

A 100 V d.c. generator supplies a current of 15 A when running at 1500 revmin. If the torque on the shaft driving the generator is 12Nm, determine (a) the efficiency of the generator and (b) the power loss in the generator.

The shaft torque of a diesel motor driving a 100 V d.c. shuntwound generator is 25 Nm. The armature current of the generator is 16 A at this value of torque. If the shunt field regulator is adjusted so that the flux is reduced by 15, the torque increases to 35 Nm. Determine the armature current at this new value of torque.

Determine the torque developed by a 350 V d.c. motor having an armature resistance of 0.52 and running at 15 revs. The armature current is 60 A.

An 8pole d.c. motor has a wavewound armature with 900 conductors. The useful flux per pole is 25 mWb. Determine the torque exerted when a current of 30 A flows in each armature conductor.

The armature of a d.c. machine has a resistance of 0.25 2 and is connected to a 300 V supply. Calculate the e.m.f. generated when it is running (a) as a generator giving 100 A, and (b) as a motor taking 80 A.

A d.c. shuntwound generator running at constant speed generates a voltage of 150 V at a certain value of field current. Determine the change in the generated voltage when the field current is reduced by 20, assuming the flux is proportional to the field current.

A generator is connected to a 60 22 load and a current of 8 A flows. If the armature resistance is 1 2, determine (a) the terminal voltage and (b) the generated e.m.f.

An 8pole, lapwound armature has 1200 conductors and a flux per pole of 0.03 Wb. Determine the e.m.f. generated when running at 500 revmin.

a. Explain how to nortonize a given circuit b.

b. By using superposition theorem,find the current in resistance R. R0.05,R0.04,R1 negligible) 0.05 Ohm 0.04 Ohm Lim 1 Ohm 2.05 V 2,15V Hill E2.05V,and E2.15V(internal resistance of the cells is (Smarks) 0.05 Ohm 0.04 Ohm Lum 1 Ohm www 2.05 V Hilt 0.05 Ohm 0.04 Ohm 1 Ohm www 2.15 V HIH

solve the following two parts of the question:

a) State two advantages of using the hparameters b) The hparameters of a transistor in CE configurations are bie1000,bre3.5x104,hfe, 55 and hoe 20uQ.if the load 2K, find the current gain and voltage gains.Comment on the value of voltage gain.(10marks) (2marks)

solve the following two parts of the question:

a) When a reverse gate voltage is 12V,the gate current is 1.6x10mA.Find the resistance between gate and source (4marks) b) Determine the value of ge for a FET if the drain current changes from 2mA to 2.2mA when gate source voltage is changed from 3V to 2.7V. (4marks) c) For a FETg30002,ra32K. Calculate amplification factor of the device(4marks)

A 4pole generator has a lapwound armature with 50 slots with 16 conductors per slot. The useful flux per pole is 30 mWb. Determine the speed at which the machine must be driven to generate an e.m.f. of 240 V.

An 8pole, waveconnected armature has 600 conductors and is driven at 625 revmin. If the flux per pole is 20 mWb, determine the generated e.m.f.

Problem 13. A resistor of 25 2 is connected in series with a capacitor of 45 F. Calculate (a) the impedance and (b) the current taken from a 240 V, 50 Hz supply. Find also the phase angle between the supply voltage and the current.

A coil consists of a resistance of 100 52 and an inductance of 200 mH. If an alternating voltage, v, given by v200 sin 500r volts is applied across the coil, calculate (a) the circuit impedance, (b) the current flowing, (c) the p.d. across the resistance, (d) the p.d. across the inductance and (e) the phase angle between voltage and current.

A coil of inductance 318.3 mH and negligible resistance is connected in series with a 2002 resistor to a 240 V, 50 Hz supply. Calculate (a) the inductive reactance of the coil, (b) the impedance of the circuit, (c) the current in the circuit, (d) the p.d. across each component and (e) the circuit phase angle.

A coil has a resistance of 4 22 and an inductance of 9.55 mH. Calculate (a) the reactance, (b) the impedance, and (c) the current taken from a 240 V, 50 Hz supply. Determine also the phase angle between the supply voltage and current.

A 6pole lapwound motor is connected to a 250V d.c. supply. The armature has 500 conductors and a resistance of 1 22. The flux per pole is 20 mWb. Calculate (a) the speed and (b) the torque developed when the armature current is 40 A.

Three impedances, Z 1000 2, Z63.2518.43 2 and Z100290 2 are connected in star. Convert the star to an equivalent delta connection.

Determine the deltaconnected equivalent network for the starconnected impedances shown in Figure 37.33 10 (2 2012 Figure 37.33 150

Replace the deltaconnected network shown in Figure 37.5 by an equivalent star connection 2 20 1 Figure 37.5 H 20120 12 10 (3

Convert the circuit shown in Figure 36.82(a) to an equivalent Norton network. (b) Convert the network shown in Figure 36.82(b) to an equivalent Thvenin circuit. OA Figure 36.82 20 V 3A (a) 08 202 B

Use Nortons theorem to determine the value of current in the circuit shown in Figure 36.56. 20 Figure 36.56 302 1302 280

If a charge on the body is InC, then how many electrons are present on the body (a) 1.6 1019 (c) 6.25 10 (b) 6.25 x 101 (d) 6.25 x 108

A metallic sphere is placed in a uniform electric field as shown in the figure. Which path is followed by electric field lines (a) A A B D (b) B (c) C (d) D

S.I. unit of (a) Farad permittivity of free space is (b) Weber (c) CNm (d) CNm

Figure shows three point charges 2q, q and 3q. Two charges 2q and q are enclosed within a surface S. What is the electric flux due to this configuration through the surface S. 4d E 3q. (b) 2d 9 2g S olu (d) 0

The total flux through the faces of the cube with side of length a, if a charge q is placed at corner A of the cube is 9 (a) 8E0 9 (b) 40 O 9 0 9 (d) 10

The sum of two points charges is 9uC. They repel each other with a force of 2N when kept 30cm apart in free space. Calculate the value of each charge. (b) 1 C and 5C (d) 5C and 4C (a) 5C and 3C (c) 3C and 5C

What is the nature of Gaussian surface involved in Gauss law of electrostatics (a) Scalar (c) Magnetic (b) Electrical (d) Vector

Two points charge q 2q are placed at the vertices B and C of an equilateral AABC of side a, as shown in figure. Find electric field at the vertex A due to these charges. (a) E3 A B (q) 9 43 a (29) C (b) (d) 9 4. 93 43 a

Two point charge q 9q are separated by a distance of 10a. Find the point on the line joining the two charge where electric field is zero.,(a) 2.5a from (q) and (7.5a from 9q) (b) 3 from (q) and 7 from 9q (c) 7.5a from (q) and 2.5a from 9q (d) 5 fromq and 5 from 9q

Two spheres of radii a and b respectively are charged and joined by a wire. The ratio of electric field of the sphere is a b (b) b a (c) b (d) a

Charge Q is divided into two parts which are then kept some distance apart. The force between them will be maximum, if the two parts are having the charge () each (b) and and 30 4 20 3 (d) e and (Qe), where e is electronic charge.