Electronic Power
Electrical Power is the energy transferred in a period of time in a circuit.
There are a few equations involving power that you need to be able to apply in National 5. These equations describe the relationships that power has with Current, Potential Difference and Resistance.
Power Equation
Electrical Power is the energy transferred in a period of time in a circuit
This can be calculated using the following equation:
Power = Energy/time
Power is measured in Watts (W)
Energy is measured in Joules (J)
Time is measured in seconds (s)
Power, Voltage, Current, Resistance
Voltage, current and resistance all impact the power across a component in a circuit. There are 3 equations that you need to be able to apply involving these 4 measurements:
Power = Current x Voltage
Power = Current^2 x Resistance
Power = Voltage ^2 / Resistance
Power (P) is measured in Watts
Current (I) is measured in Amperes
Voltage (V) is measured in Volts
Resistance is measured in Ohms
It’s very important to identify the given values in exam questions and apply them to the correct equations.
Fuses
Fuses are components that break if current gets too high. This is very important as it maintains the safety of electrical appliances. All plugs that go into the the mains supply (230V) have a fuse that can be replaced. These fuses prevent the plug from overheating and potentially starting a fire.
You need to select the correct fuse for a circuit depending on the Power value of the circuit.
For appliances that have power up to 720W, you use a 3 Amp fuse.
For appliances that have power over 720W, you use a 13 Amp fuse.
Key Points!
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Power
Power is the rate at which energy is transferred.
It can be calculated using the equation P=E/t
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Power equations
Apply and rearrange the following equations:
P = IV
P = I^2R
P=V^2/R
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Fuses
Fuses protect a circuit when current gets too high.
For appliances that have power up to 720W, you use a 3 Amp fuse.
For appliances that have power over 720W, you use a 13 Amp fuse.