# edexcel P2 topic 2

-circuits

-current and voltage

-resistance

-energy transfer in resistors

- Created by: bleona
- Created on: 29-10-12 14:41

First 340 words of the document:

TOPIC 2- controlling and using electric current

Series and Parallel circuits

Series circuit components connected on the same loop of the circuit. The current that flows across each

component is the same.

Parallel circuit components connected on separate loops. The current is shared between each

component and the total current entering a junction is equal to the total current leaving a junction. The

current is described as being conserved.

Current and voltage:

Current is the rate of flow of charge around a circuit and it is measured in amperes (A) by an ammeter which

must be connected in series.

Voltage (potential difference) is the driving force that pushes the current around the circuit and it is measured

in volts (V) by a voltmeter must be connected in parallel.

If you increase the voltage then the more current will flow.

Potential difference is the energy transferred per unit charge passed.

The bigger the change in voltage, the more energy is transferred.

Equation: Energy transferred (joule, J) = potential difference (volt, V) x charge (coulombs, C)

Resistance:

Resistance is a measure of how hard it is for a current to flow through a component. Resistors are added to

reduce the flow of current.

If you increase the resistance, then less current will flow.

Bulbs have resistance, so if you add more bulbs the resistance increases therefore the current decreases.

A variable resistor (rheostat) is a device with variable resistance and it is used to vary the amount of current

in a circuit.

Voltage, Current and Resistance

The size of current depends on the voltage driving it and the amount of resistance.

If you increase resistance, the current decreases.

If you increase potential difference, then the current also increases.

Equation: resistance (ohm, ) = voltage (volts, V) x current (amperes, A)

Resistance graphs:

Voltage Current graphs show how current varies as you change the voltage.

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