01012022 Current potential difference power and resistance Lesson

01/01/2022 Current, potential difference, power and resistance Lesson 2: Current, Voltage, Resistance and Circuit Rules (Summary Notes pages 7 -11) Electricity M Ashton 2013

What are we learning today? �A review of current, voltage, ohm’s law and series and parallel circuits. �An alternative unit for the volt. �To review the relationships: Q= It V = IR RT = R 1 + R 2 + R 3

Current �This is the flow of charge (electrons) in a circuit and always flows from negative to positive. Current is measured in amperes, A, using an ammeter. �Current is defined as the flow of charge per second and is given by the equation

Now complete SAQ 6 on p 3.

Voltage �Voltage is a measure of the energy given to the charges in a circuit. �A voltage of 6 V means that 6 joules of energy is given to each coulomb of charge in the circuit. �The electrical energy supplied is transformed into other forms of energy in the components that make up the circuit.

�Voltage is measured in volts, V, using a voltmeter. �Voltage is defined as the energy transferred per unit charge and is given by the equation �This gives an alternative unit for voltage. 1 V = 1 JC-1

Now complete SAQ 7 on p 3.

Ohm’s Law �In any circuit providing the resistance of a component remains constant, if the potential difference, V, across the component increases the current, I, through the component will increase in direct proportion. �This is summarised by the equation A resistor can be used to limit the current in a circuit.

Now complete SAQ 8 on p 3.

Series and Parallel Circuits �In order to progress successfully in this course you must know the circuit rules for series and parallel circuits. �These are summarised below. Current Series IS = I 1 = I 2 =I 3 Voltage VS = V 1 + V 2 + V 3 Resistance RS = R 1 + R 2 + R 3 Parallel IP = I 1 + I 2 + I 3 VP = V 1 = V 2 = V 3

Now complete SAQ’s 9 and 10 on page 4.