P4: Electric circuits Flashcards
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.
How do we calculate resistance in a series circuit
Add up all of the individual resistors together
How is a battery made
Combining cells
How do we calculate voltage in a series circuit
Add up all of the individual voltages together
What is a parallel circuit
A circuit that has its components connected in separate branches of wires to the energy source. In parallel, voltage is the same across everywhere.
How does current work and how do we work it out in parallel
Current through battery is larger than all of the individual currents. To work out the total current, add all of them up individually. It should equal the total current in the supply.
How do we work out the resistance in parallel
The combined resistance of two resistors in parallel is less then the resistance of the resistors individually. To work out the total resistance, deduct the individual resistors together
What happens to the lamp in parallel
Each lamp can switched off or on separately. However if 1 lamp breaks, current can still flow through the others.
What is the equation for power
Energy transfer/Time
What is the other equation for power
Current X Current X Resistance
What are two other equations for power
Voltage x Current
Current X Current X Resistance
What is Ohms Law?
Current through an ohmic conductor is directly proportional to the voltage across the resistor. This means the resistance remains constant as the current changes
