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C12.1 Current and charge AQA AS Physics C12 Electricity Kerboodle Answers: Page No. 203

1.Ans- a i) 3.5 c ii in 10 min. 210 c b Calculate the average current in a wire through which a charge of 15 C passes in i ss, 3.0A ii 100 s. 0.15 A 2.Ans- a HA 3.8x 1015 b S.OA. 1.9 x 1022 3.Ans- a the charge flowing along the beam each minute 72 mC b the number of electrons that pass along the beam each minute. 4.5 x 1017 4 .ANS- 1600 s b 0.1 A. 8000 s

12.2 Potential difference and power AQA AS Physics C12 Electricity Kerboodle Answers : Page No. 205

1. 29kJ b O.OSX 720J 2.a )the current through the light bulb 2.0A b the energy transfer to the light bulb in 1800 s. 22kJ 3. i) 48kJ ii 3.5A 4.a) 12 kJ b. 4.5W c 2700s

12.3 Resistance AQA AS Physics C12 Electricity Kerboodle Answers: Page No. 208

1. 6.0.0, I OV, 0.125 mA, 160.0, 2.5 mA b 7.5.0 2.Ans- 310 3.Ans- o.11mo 4.a 1.8 x10-6 nm b33mm

12.4 Components and their characteristicsAQA AS Physics C12 Electricity Kerboodle Answers : Page No. 211

1.a.0.25A, 12D b The filament would become brighter and hotter until it melts and breaks as a result. 2.Ans- a at20’C 0.03mA 3.a. b The diode would then be ‘reverse-biased’ so the current in the circuit would be negligible. 4.a. the resistance at SO ‘C 30.4 n b. the temperature when the resistance is 30.00. 46°C Baneer 6

Practice questions: Page No. 212-213

(b) (c) 2 .(a) ΔQ = I Δt = 40 × 10-3 × 3 × 60 = 7.2 C (b) (c) (d) 3 (a) (b) Current is zero for all negative voltages For positive voltages, curve showing a steep rise in current starting at about +0.6 V (with voltage not greatly to exceed 1 V) 4. . (a) (i) Readings need to be taken more quickly than could be achieved by manual timing (ii) Rate: more than 40 samples per second Reason: the current rises very rapidly over the first 0.1 s, and you should have about 4 results on this first section (b) Initial resistance is low so initial current is high • Temperature of filament increases (or filament heats up) • Resistance increases as temperature rises • Increase in resistance causes current to fall • Current is steady when energy supplied = energy lost from filament (or when temperature is constant) • Maximum heating is produced at start when current is highest • Melting of filament causes it to fail (could be mechanical failure caused by temperature rise) • When switched on energy is supplied more rapidly than it is lost so filament melts 5. (a) (b). 6. (a) (i)Circuit to show: • Battery, switch, wire, variable resistor and ammeter in series • Voltmeter in parallel with wire (ii) Switch on, measure I and V Change length of wire Measure new I and V Measure length of wire each time (iii) (b) 7 (a) (i) A component (or substance) which has no electrical resistance (ii)• Correct high temperature graph with abrupt discontinuous vertical line indicating that R has become zero at a certain temperature • Temperature axis labelled (e.g. Transition) at the corresponding temperature (b) Reason: When resistance is zero there is no energy (heat, or power) lost Applications: Power cables, electromagnets, generators, motors, transformers, MRI scanners, monorail trains, particle accelerators, fusion reactors. Banner 7

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