# CIE AS & A Level Physics : 9.1 Electric current – Exam style question – Paper 1

### Question

For a current-carrying wire, the current can be calculated using the equation shown.

I = Anvq

What is the meaning of n?

A    the number of charge carriers in the wire

B    the number of charge carriers multiplied by the volume of the wire

C    the number of charge carriers per unit length of the wire

D    the number of charge carriers per unit volume of the wire

Ans:

### Question

The number of free electrons passing a point in a wire in 24 hours is $$6.0\times 10^{23}$$.

What is the average current in the wire?

A    $$6.3$$ pA        B   $$1.1$$A            C     $$67$$A         D    $$4.0$$ kA

Ans:

### Question

What is meant by electric field strength?
A force per unit charge acting on a small mass
B force per unit charge acting on a small positive charge
C force per unit mass acting on a small mass
D force per unit mass acting on a small positive charge

Ans:

### Question

The current I in a wire is given by the equation
I = nAvq
where n is the number density of the free electrons, A is the cross-sectional area of the wire, v is the average drift velocity of the free electrons and q is the charge of an electron. Which relationship is not used in the derivation of this equation?
A charge = current × time
B distance = speed × time
C number = number density × area
D volume = length × area

Ans :

### Question

Which two units are used to define the coulomb?
A  ampere and second
B  ampere and volt
C  volt and ohm
D  volt and second