Can you define current, potential difference and resistance in a circuit, and give their units?

Current is the flow of charge in the circuit, a bit like the flow of water in a river, and is measured in Amps (A).

Potential difference is defined as the 'work done per unit charge', which is related to the voltage across (and so the energy supplied to) a component in the circuit. It's measured in Volts, (V).

Resistance is the quantity that describes how difficult it is for a current to flow in a circuit (think of traffic trying to get through a narrow tunnel vs a motorway), and is measured in Ohms, (Ω).

Bonus: do you know the relation between these three quantities? 

A: it's called Ohm's law, and it states that R=V/I, or resistance is potential difference divided by current.

Rosemary T. A Level Maths tutor, GCSE Maths tutor, A Level Physics tu...

5 months ago

Answered by Rosemary, a GCSE Physics tutor with MyTutor

Still stuck? Get one-to-one help from a personally interviewed subject specialist


£18 /hr

Ayusha A.

Degree: BEng electrical and electronics engineering (Bachelors) - Newcastle University

Subjects offered: Physics, Maths+ 1 more

Further Mathematics

“About me: I am a final year Electrical and Electronic Engineering student at Newcastle University. I took Mathematics, Further Mathematics, Chemistry and Physics as my A-level subjects. I did peer mentoring in university and also have...”

£18 /hr

Carys L.

Degree: Architectural Engineering (Masters) - Cardiff University

Subjects offered: Physics, Maths


“I am currently in my second year, studying Architectural Engineering at Cardiff University. It's very different to the subjects offered at school, but I believe that a good understanding of the subjects I was learning is what helps me...”

£20 /hr

Jonas P.

Degree: MPhys Theoretical Physics (Bachelors) - Edinburgh University

Subjects offered: Physics, Maths


“I am currently a student at the University of Edinburgh, doing my 4th year of the MPhys Theoretical Physics programme. I've managed to score an average grade of 81% in year 3, and I tend to consistently do well in my exams, which I be...”

About the author

Rosemary T.

Currently unavailable: for regular students

Degree: Physics (Masters) - Durham University

Subjects offered: Physics, Maths


“Hello,  I'm Rosemary, a third-year Physics student with four years' experience in tutoring, first through a school mentoring scheme and then through my University's one-to-one tutoring project. I like to use analogies to help student...”

You may also like...

Posts by Rosemary

Can you define current, potential difference and resistance in a circuit, and give their units?

Use the chain rule to differentiate y=(x-3)^(-3)

Other GCSE Physics questions

Two identical objects have a charge of magnitude q. If r is the distance bethween them, what should their mass be so that the objects are balanced.

What is the mass of an object travelling at 15 m/s with a kinetic energy of 100 J?

Define electric current

Explain the process of nuclear fission.

View GCSE Physics tutors


We use cookies to improve our service. By continuing to use this website, we'll assume that you're OK with this. Dismiss