Electricity Flashcards
What is the independent variable in investigating the resistance in a wire?
The length of the wire
What is the dependent variable in investigating the resistance in a wire?
The resistance
What is the control variable in investigating the resistance in a wire?
Type of metal or diameter of the wire
What is the conclusion of investigating the resistance in a wire?
As the length of the wire increases, the resistance of the wire also increases.
What is the independent variable in investigating series and parallel circuits with resistors?
The circuit type (series and parallel)
What is the dependent variable in investigating series and parallel circuits with resistors?
The resistance
What is the control variable in investigating series and parallel circuits with resistors?
Number of resistors, type of power source
What is the conclusion of investigating series and parallel circuits with resistors?
Adding resistors in series increases the total resistance of the circuit. In a parallel circuit, the more resistors you add, the smaller the resistance.
What does 1kW equal?
1000W
What does 1000W equal?
1kW
What does 0.5kW equal?
500W
What does 500W equal?
0.5kW
What is electric current?
The flow of electric
charge. It only flows when the circuit is complete.
What is charge?
The current flowing past a
point in a given time.
What is charge measured in?
Coulombs (C)
Describe an ohmic conductor.
The current is directly proportional to the potential difference - it is a straight line (at a constant temperature).
Describe a filament lamp.
As the current increases, so does the temperature. This makes it harder for the current to flow. The graph becomes less steep.
Describe a diode.
Current only flows in one direction. The resistance
is very high in the other direction which means no current can flow.
What is potential difference (voltage)?
The push of electrical charge.
What does resistance do?
Slows down the flow of electricity.
What does LDR stand for?
Light dependent resistor.
What is an LDR dependent on.
Light intensity
Describe resistance in an LDR.
In bright light the resistance falls and at night the resistance is higher.
What are uses of LDR’s?
Outdoor night lights, burglar detectors.
What is a thermistor?
A temperature dependent resistor
Describe the resistance in a thermistor.
If the thermistor is hot, then the resistance is less. If the thermistor becomes cold, then the resistance increases.
What is a use of a thermistor?
A thermometer (temperature detectors).
What happens if a component is broken in a series circuit?
All the other components will stop working.
Describe potential difference in a series cicuit.
The total p.d. of the supply is shared between all the components.
Describe current in a series circuit.
Wherever the ammeter is placed in a series circuit the reading is the same.
Describe resistance in a series circuit.
The resistance will add up to make the total resistance.
Are series or parallel circuits more useful?
Parallel - If one component stops working it will not affect the others.
Describe potential difference in parallel circuits.
The same for all components.
Describe current in parallel circuits.
The total current is the total
of all the currents through all the components.
What does adding the resistance do to parallel circuits?
Adding resistance reduces the total resistance.
What is the UK mains supply?
230V
What is the UK frequency?
50 hertz
What is AC?
Alternating current - constantly changing direction.
What is DC?
Direct current - Supplied by batteries and only flows in one direction.
What are the 3 wires in cables?
Live, neutral and earth.
What does the live wire do?
Provides the potential difference from the mains.
What does the neutral wire do?
Completes the circuit.
What is the national grid?
A system of cables and transformers.
What do step - up transformers do?
Increase the voltage as the electricity flows through the cables.
What do step - down transformers do?
Decrease the potential difference to make it safe for consumers.
