9.2 Potential difference and electromotive force

Question 1

What is potential difference?

Answer 1

Voltage, also known as potential difference (p.d.), is a measure of the electrical energy transferred per unit charge. In other words, the energy transferred by the charge carriers. It can be defined as the amount of work done per unit charge and is calculated using:
V = W/Q
V= Voltage
W=Work done
Q=charge

Question 2

How is voltage measured?

Answer 2

Voltage is measured as a difference in potential between two points, thus a voltmeter must be connected in parallel and is used to measure the difference in potential across a device.

Question 3

What must the resistance of a voltmeter be and why?

Answer 3

Approx. ∞Ω, to prevent a short circuit.

Question 4

What is electromotive force?

Answer 4

Electromotive force (e.m.f) is the energy transferred to the charge carriers by the cell/ battery/ power supply. E.m.f is expressed in volts and is calculated similarly to p.d.:
ε= W/Q
ε=e.m.f.
W=W.d.
Q=charge