TUTORIAL 1 & ASSIGNMENT 1 QUESTIONS

QUESTION 1 

1.1 Two wires are identical, except that one is aluminum and one is copper. The aluminum wire has a resistance of 0.20 ῼ. What is the resistance of the copper wire? (4)

1.2 A cylindrical wire has a length of 2.80 m and a radius of 1.03 mm. It carries a current of 1.35 A, when a voltage of 0.0320 V is applied across the ends of the wire. From what material is the wire made? Consult resistivity Table 20.1  (5)

QUESTION 2

2.1 Suppose a single electron orbits about a nucleus containing two protons (+2e), as would be the case for a helium atom from which one of the two naturally occurring electrons is removed. The radius of the orbit is 2.65 x 10 ^-11m. Determine the magnitude of the electron’s centripetal acceleration.                                                                                                                                                                    (8)

2.2 A single electron orbits a lithium nucleus that contains three protons (+3e). The radius of the 

 orbit is 1.76 x 10 ^-11m. Determine the kinetic energy of the electron. (8)

QUESTION 3

The drawing below shows an equilateral triangle, each side of which has a length of 2.00 cm. Point charges are fixed to each corner, as shown. The 4.00 µC charge experiences a net force due to the charges q_A and q_B. This net force points vertically downward and has a magnitude of 405 N.

Determine the magnitudes and algebraic signs of the charges q_A and q_B.  (8)

                                                                                                                                                             

QUESTION 4

4.1 The drawing shows three point charges fixed in place. The charge at the coordinate origin has a value of q1 = +8.00 µC; the other two charges have identical magnitudes, but opposite signs:

q₂ = – 5.00 µC and q₃ = + 5.00 µC.

(a) Determine the net force (magnitude and direction) exerted on q₁ by the other two charges. (6)

(b) If q₁ had a mass of 1.50 g and it were free to move, what would be its acceleration? (2)

4.2 Three charges are placed on the x-axis. The charge q₁ = +2.0 µC is placed at x = 0.0 m and the

 charge q₂ = +5.0 µC is placed at x = 2.0 m.

Determine the position on the x-axis where q3 should be placed to achieve a resultant electric force of zero. Let the distance between q3 and q1 be .

(6)

4.3 P; R and S are three point charges and interact as shown below.

4.3.1 Draw the Free body diagram (Vector diagram) for charge (3)

4.3.2 Calculate the net electrostatic force on charge P due to fields of R and S (10)

4.3.3 Describe any FIVE properties of electric field lines to your Grade 11 learners. 

 Draw annotated sketch to support your answer. (5)

If charge P is removed while R and S remains; Draw/ sketch

4.3.4 the electric field lines between R and S (4)

4.3.5 the graph relating the force and distance between R and S according to Coulomb’s Law. (2)

4.4 The sketch shows two small metal spheres A and B distance r from their centers and placed on insulated stands. The charge of spheres are q and 2q respectively. Sphere A exerts a force of F on B. What is the magnitude of the force that sphere B exerts on A? The spheres are now placed a distance ¼ r apart. Determine the magnitude of the electrostatic force each sphere experiences. (5)

QUESTION 5

1.  A negative charge of 2nC is 10 cm from point P. P

– 2nC 10 cm 

1.  Define electric field at a point                                                                        (2)
2. A positive charge is of 3 nC is now positioned 5 cm from point P, as showed in the diagram below

P

10 cm 5 cm

– 2nC 

3 nC

Calculate the magnitude of electric field at P due to both charges (12)

5.2 Use the information in the diagram below to find the electric field at x = -1.0 m; y = 0 m
	(9)

5.3 Drawn in the diagram below are two separate electric fields, field a and b.

Identify the nature of each charge, and estimate the relative magnitude of the charges. Explain your answer.  (9)

QUESTION 6 [ ELECTRIC FIELD STRENGTH AND ELECTRIC POTENTIAL]

6.1 State the principle of superposition of vectors in words     (2)

6.2 Two electric charges are located as follows: q₁ = + 30C at (0,0) and

 q₂ = – 40 C at the point (0,3). Point P is located at (2,1)

1. Draw an annotated sketch to show the position and orientation of q₁; q₂ and point P in the x - y plane. Indicate the direction of the electric fields as lines of force.                                                 (5)
2. Determine the net electric field strength at position (2,1) due to q₁ 

and q₂ .                                                            (8)

QUESTION 7 [ ELECTRIC FIELD STRENGTH AND ELECTRIC POTENTIAL]

7.1

Find the magnitude and direction of the NET electric field at the origin of the coordinate system due to the two-point charges, q1 and q2. The two charges are located at the x-y coordinate position of (0.0, -2.0 cm) and (+4.00 cm, 0.0), respectively, as shown in the figure.

(8)

7.2  Find the electric potential, taking zero at infinity, at the empty corner in the rectangle below
	(8)

7.3 

Two point charges are held at the corners of a rectangle as shown in the figure. The lengths of the sides of the rectangle are 0.050 m and 0.150 m. Assume that the electric potential is defined to be zero at infinity

QUESTION 8 [ WORK DONE IN ELECTRIC FIED & ELECTRIC POTENTIAL]

8.1	A particle has a charge of +1.5 µC and moves from point A to point B, a distance 0f 0.20 m. The particle experiences a constant electric force, and its motion is along the line of action of the force. The difference between the particle’s electric potential energy at A and at B is EPEA – EPEB = +9.0 x 10-4 J.
		Find the magnitude and direction of  the electric force that acts on the particle (5) the electric field that the particle experiences (5)
8.2		An alpha particle has a positive charge of 2e and a mass of 6.6 x 10-27 kg. With what velocity would an alpha particle reach the negative plate of a parallel plate apparatus with a potential difference of 2.0 x 103 V, if it started, at rest, next to the positive plate?	(6)

QUESTION 9

Three charges are at the corners A, B and C of an equilateral triangle. Each charge has a value of +5.00 nC. The length of each side of the triangle a = 4.00 cm. Calculate the electric potential at the midpoint of the base BC. Provide your answer in units of kV.

(10)

 

QUESTION 10 [ GAUSS LAW & COULOMB’S LAW]

10.1 State Gauss Law in words                                                                  (2)

10.2 Two gaussian spherical surfaces X and Y of radii 5 cm and 7cm 

 respectively, are placed distance d from their circumferences. The 

 charges of each are as indicated in the diagram. The electric field 

 strength at Y is 3,5 x 10 ^{– 12} NC ^{– 1}.

d

X Y

 10C – 20 C

 Determine 

 10.2.1 the force of attraction or repulsion between X and Y (7)

 10.2.2 the net electric field flux due to X and Y. (6)

FORMULA SHEET FOR PHSE 322

_{F = ma}

+y 1.30 m 23.0 23.0 92 1.30 m 93 -+x