Electric Current - exam practice

The current in a wire is 20 mA.

How many electrons pass a point in the wire in 2 minutes?

The diagram shows the currents in a set of wires.

What is the magnitude of the current at X?

A gas containing doubly-charged ions flows to give an electric current of 0.64 A

How many ions pass a point in 1.0 minute?

A mobile phone operates at a constant power of 200 mW

It has a 3.7 V lithium-ion battery that has a charge capacity of 9,400 C

What is the time taken for the battery to discharge completely?

Which electrical quantity has S.I. units ampere-second (As)?

The diagram below shows the motion of positive and negative particles in a conducting solution.

Which statement is correct?

One million electrons travel between two points in a circuit.

The total energy gained by the electrons is 1.6 × 10⁻¹⁰ J.

What is the potential difference between the two points?

The diagram shows the conventional currents entering and leaving a junction in an electric circuit.

I₁ , I₂ , I₃ and I₄ are all positive.

Which statement is always true?

A copper wire is connected across a cell. The conduction electrons within the copper wire move.

Which statement is correct about these electrons?

One of Kirchhoff’s laws is stated below.

The sum of the currents entering a point in a circuit is equal to the sum of the currents leaving the same point.

Which quantity is conserved according to this law?

The potential difference across a lamp is 2.5 V. The current in the lamp is 20 mA.

What is the energy dissipated in the lamp in 3.0 hours?