electrical circuits on 3.2 Questions 1 What is the internal resistance of a 6 V battery if it supplies 58V.toa lamp when the current flowing is 0.40 A? 2 What is the internal resistance of a 1.5v dry cell, that delivers 13% to a lamp which has a resistance of 5.0 07 3 The starter motor for a car engine needs a very high current, for example 100 A. resistance. (a) Explain why a car battery should have a very low internal (b) Explain why the car's headlights are observed to dim if they are on when the car's starter motor is used. A student investigating the emf and internal resistance of a dry cell used the circuit in fig B, with the cell in the place marked by the dashed lines. She collected the results in table A. Plot a graph to find both the internal resistance and the emf of the cell that the student tested. Ammeter reading, I/A Voltmeter reading, V/V 0.10 1.45 0.20 1.42 fig B Circuit for demonstrating the effect of internal resistance 0.30 1.39 0.40 1.31 0.80 1.18 1.10 1.09 table A Current and voltage readings from a student experiment to internal resistance of a dry cell. Questions 1 How much work in done by the reshtor in the circuit in fig I If the grout h sailed on for 19 prounds! power Reply reuter volumeter 2 what is the power dissipated by the resistor in fig E? 3 what power is dissipated by a 470 Il resistor where [a] current of 1 76 A passes through it? to) it is measured with a pd of 9.OV? 4 (a) what is the efficiency of the electric heater in fig F (b) Why would your answer to part (a) be the same if you consider the heater switched on for one hour, and if you consider it switched on for two hours? 100J of 1 J of light 4 J of sound energy electrical energy energy useful energy output - energy input 95J of heat energy fig F Energy flows through an electric heater. 5 Compact fluorescent lamps have a tube containing a gas, which glows when electricity passes through it. These are much more efficient than filament, lamps in which a metal wire glows when it is red hot due to the ohmic heating current flow through it. Explain why compact fluorescent lamps are much more efficient than filament lamps