Resistance: Calculations in Electric Circuits

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This note covers the calculation of resistance, voltage and current in electric circuits. It is ideally used in conjunction with the mind map on resistance.
tatemae.honne
Note by tatemae.honne, updated more than 1 year ago More Less
alex.examtime9373
Created by alex.examtime9373 over 11 years ago
tatemae.honne
Copied by tatemae.honne over 11 years ago
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Current in a series circuitThe current is the same at every point along the wire

Current in a parallel circuit Different-sized currents can flow through parallel parts of a circuit The current before and after the parallel section of circuit is the same

The sum of the currents entering a point in a circuit equals the sum of the currents leaving it I = I₁ + I₂ + ...

Voltage in circuits The potential difference of the full circuit equals the sum of all the potential differences in the circuit V = V₁ + V₂ = ...

Resistance in circuits

Resistors in series:R = R₁ + R₂Derivation: Based on V = V₁ + V₂ The two resistors are connected in series, so the same current flows through both IR = IR₁ + IR₂ (Since V = IR) R = R₁ + R₂ (by dividing by I)

Resistors in parallel1/R = 1/R₁ + 1/R₂Derivation Based on I = I₁ + I₂ The potential difference between two points is the same regardless of the path followed (=V) V/R = V/R₁ + V/R₂ (since I = V/R ; Ohm's law) 1/R = 1/R₁ + 1/R₂ (by dividing by V)

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1 comment

about 10 years ago
Thank you for this piece of work, really helpful for revision!

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