P4: Electric circuits
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What is current
Flow of charge in a circuit
What is current measured in
Amperes
How do we calculate charge flow
Current X Time
How can an electric charge be able to flow
There must be a potential difference source and a closed or complete circuit.
What is an electrical conductor
A material that allows electric current (flow of charge) to pass through. It conducts electricity
What is an electrical insulator
A material that doesn’t allow electric current (flow of charge) to pass through. It doesn’t conduct electricity. It has no delocalised electrons
What is electric current through a metal
Flow of delocalised electrons
What is potential difference (voltage)
The pushing force of current in a circuit
What is voltage measured in
Volts
What do we use to measure current
Ammeter
What do we use to measure voltage
Voltmeter
What is resistance
The slowing force of current in a circuit
What is resistance measured in
Ohms
What is the effect linking voltage, current and resistance
If voltage is increased, current is increased and resistance is constant. To measure resistance of a component, measure the voltage of a component. The longer the wire, the higher the resistance.
What is the equation to work out resistance
Voltage/Current
What are the results if we plot a current voltage graph
As the voltage is increased, the current is increased. It also obeys Ohms Law as it states it is a straight line. The slope of the graph is 1/resistance. It shows that the resistance is constant.
What are the results if we plot a filament bulb graph
The gradient will decrease at larger potential differences. When current through a filament (thin wire) lamp increases, temperature of lamp increases. This increases resistance of the lamp and causes a curve in the graph
What is a diode
Diodes are components that allow current to flow in one direction
What is a rectifier
Rectifiers are components that turn an alternating current into a direct current. Diodes act as rectifiers as they break the alternating current when changing direction
What is a thermistor
A component where resistance changes with its temperature. Usually increasing temperature decreases resistance. Thermistors can be used to turn a heater off when a house reaches a certain temperature
What is an LDR
Light Dependent Resistor. The resistance changes with light intensity. An LDR can switch lights on when its dark
What does the energy source do in an electric circuit
Provides electrical energy to a bulb which radiates that energy as light and heat energy
What is an ohmic conductor
A conductor that obeys Ohm’s Law. It has a constant resistance. Current through an ohmic conductor (at constant temperature) is directly proportional to potential difference across a resistor
What is a series circuit
A circuit with all its components connected on the same line as each other. In series, current is the same.