How to i calculate total resistance in a circuit?

Total resistance in a circuit depends on whether the resistors are in series or parallel since this determines which equation is to be used.In series, resistors are essentially lined up next to each other so the total is simple since it is just the sum of the resistors resistance in ohms.e.g. if a circuit has one 10ohm, one 45ohm and one 235ohm resistor in it, all three of which are in series, the total resistance is (10+45+235)ohm = 290ohmsIn parallel each resistor is on its own path for the electricity to follow and as a result the equation is not quite the same, we use the equation: 1/Rtotal = 1/R1 + 1/R+ 1/R..etce.g. a circuit has 3 resistors all in parallel. Their resistances are 25ohm, 5ohm and 100ohm respectivley, what is the total resistance of the circuit?1/Rt = 1/25 + 1/5 + 1/1001/R= 4/100 + 20/100 + 1/1001/R= 25/100100 = 25RtR= 4ohmsoften the answer will be a fraction when calculating a parallel due to the fractions involved in the total calculation however i used a simpler calculation for the example to demonstrate the equation's use

MK
Answered by Matthew K. Physics tutor

18144 Views

See similar Physics GCSE tutors

Related Physics GCSE answers

All answers ▸

Why does lowering the control rods in a nuclear reactor reduce the amount of energy released each second from the nuclear fuel?


Explain the input and output energy sources for a car engine. How would you calculate the efficiency? Explain in terms of the inputs and outputs how the efficiency could be improved.


A person swims from a depth of 0.5m to 1.7m below the surface of the sea. Denisty Sea Water = 1030 kg/m^3. g=Gravitational Field Strength = 9.8 N/kg. Calculate the change in pressure on the swimmer and give the unit.


Draw a distance-time, speed-time, and acceleration-time graph for an object moving at a constant velocity of 5m/s for 10 seconds.


We're here to help

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

MyTutor is part of the IXL family of brands:

© 2026 by IXL Learning