How do you work out the work out the current through resistors in parallel?

[I would use the whiteboard to draw diagrams as I was talking]
A good analogy for circuits is that of water pipes. The wires are nice wide pipes with no resistance to flow. Resistors are sections of narrow pipe that restrict flow. A pressure difference (a.k.a. voltage) is needed to push water through these narrow sections. Really small pipes require high potential differences to push water through at the same rate - this is the origin of the equation V = IR.
What would happen if you get two pipes next to each other? [work through logic with student: answer is that the effective pipe width doubles]. The "effective pipe width" is called conductance, and is equal to 1/R. From the diagram, it is clear to see you simply add these conductances together, which is what you do in circuits: 1/R = 1/R1 + 1/R2. This will give you the overall conductance, and you take the reciprocal to get the resistance!

Answered by Physics tutor

1693 Views

See similar Physics A Level tutors

Related Physics A Level answers

All answers ▸

What do I need to do for full marks on the question "describe an everyday circumstance where resonance occurs (4 marks)"?


What are quarks?


What are the similarities and differences between an elastic and an inelastic collision?


Do heavy things fall faster than small things?


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences