# Electricity notes

Notes on Unit 1 of AS AQA Physcis A

- Created by: BigLebowski
- Created on: 03-03-15 19:19

First 286 words of the document:

Electricity

Electricity

The flow of electrons around a complete circuit

Conventional current

As electricity is the flow of electrons, which are negatively charged, the flow of the current

is from negative to positive

However before this was discovered the opposite was thought. Therefore conventional

current is used despite it being incorrect.

Current

Current is the rate of the flow of charge around a circuit. It is measured in amperes.

The equation: Q=I*t can be used to connect these

Charge (c)= Current (A) * time (s)

To find the Number of electrons flowing past a point, use the following:

Charge (C)/charge of an electron. This is expressed as Q/e.

For example:

1.65 c / 1.6 x 10-19

This equals 1.03 x 1019

Series and parallel circuits

In series circuits, the current is the same throughout

In parallel circuits, the current is shared between branches in proportion to the

resistance of each branch. The path of least resistance will have the greatest

current flowing through it.

Potential difference

Opposite charges attract. If the positive charge is fixed but the negative is able to move, the

potential energy which the negative charge has will decrease as it travels towards the positive.

This is the potential difference-from starting at the negative side to leaving at the positive side.

In a circuit, the cell supplies the energy required to move the electrons. Without this source of

energy, no work is done to move the electrons. How much charge goes into the component and

how much goes out is the potential difference.

Emf

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