# Electricity

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Current

Current- rate of flow of charge. Charged particles are known as charge carriers I=Q/T

Key Tips:  Whilst working out the number of electrons in an equation you have to divide the charge by 1.6 x 10^(-19)

Charge Carriers in different materials

• In insulators there are no delocalised electrons therefore when a potential difference is applied to the matreail there will be no flow of chage because the electrons are not free to move
• In metalic conductors electrons are delocalsied and surround the proton in a sea of elcectrons so when a pd is apllied it pushes the the already free elctrons to move towards positive end
• In semi conductors only some of the electrons are delocalised. They have a negative temperature coefficiant this is because as the temperature increase the value for current also inceases as more electrons cane become free

Potential difference and power

Potenial difference- is defined as work done per unit charge V=W/Q

EMF- the electrical energey produced per unit charge

Work done (J)   =    Current   x    Voltage   x  Change in Time

Power (W)  =    Current x Voltage

Resistance

Resistance- is defined as R = V/I

You can measure the affects of a change in resistance by making a simple circuit with a variable and fixed resistor also with a voltmeter and ammeter

• Variable resistor is there to make sure that there will be diferrent