Physics AS/A level Electricity

The current I in a conductor is given by the equation shown. What does the letter n represent in this equation?

• charge carried per charge carrier

• number of charge carriers per unit area

• number of charge carriers per unit volume

• total mass of charge carriers per unit volume

Which charge can be carried by a charge carrier?

• 1.1 x 10^–19 C

• 4.0 x 10^–19 C

• 4.8 x 10^–19 C

• 9.1 x 10^–19 C

The electric current in a metal wire is 4.0 mA. How many electrons pass a fixed point in the wire in a time of 10 hours?

• 2.5 x 10^17

• 2.5 x 10^20

• 9.0 x 10^20

• 9.0 x 10^23

A wire carries a current of 0.10 µA. The potential difference across the wire is 10 mV. How much energy is dissipated by the wire in a time of 10 s?

• 1.0 pJ

• 10 pJ

• 1.0 nJ

• 10 nJ

A resistor of resistance R is connected across a cell of electromotive force (e.m.f.) E and negligible internal resistance. Which single change to the circuit would lead to the largest increase in the power dissipated in the resistor?

• doubling the value of E

• doubling the value of R

• halving the value of E

• halving the value of R

In the circuit shown, the battery has an electromotive force (e.m.f.) of 6.0V and negligible internal resistance. The three resistors each have resistance R. The total power dissipated in the resistor network is 24W. What is the value of R?

• 0.50 ohm

• 1.0 ohm

• 1.5 ohm

• 2.3 ohm

The diagram shows a network of resistors. Each resistor has a resistance of 6.0Ω. What is the total resistance of the network between points X and Y?

• 3.0Ω

• 5.0Ω

• 7.2Ω

• 18Ω

Which graph could show how the resistance R of a filament lamp varies with the applied potential difference (p.d.) V, as V is increased to the normal operating p.d.?

• A

• B

• C

• D

The potential difference across a metal wire is kept constant. The length l and the diameter d of the wire are both varied. The type of metal is kept the same. How is the current in the wire related to l and d ?

• It is directly proportional to l and inversely proportional to d

• It is directly proportional to l and inversely proportional to d^2 .

• It is inversely proportional to l and directly proportional to d

• It is inversely proportional to l and directly proportional to d^2 .

Some resistors and a battery of electromotive force (e.m.f.) E and negligible internal resistance are connected in series, as shown. Which statement is correct?

• The e.m.f. across each resistor equals the potential difference across the battery.

• The potential difference across each resistor equals the e.m.f. E of the battery

• The sum of the e.m.f.s across the resistors equals the potential difference across the battery

• The sum of the potential differences across the resistors equals the e.m.f. E of the battery.