Electricity Flashcards
What is current?
The rate of flow of charge.
What is potential difference?
The energy transferred per charge.
What is resistance?
How hard it is for current to pass through a component.
What are the units for charge?
Coulombs (C)
What is the rule for current in series?
Is the same at any point in the circuit.
What is the rule for current in parallel?
The current splits at junctions
What is the rule for potential difference in series?
The potential difference across the components adds up to the potential difference across the power supply.
What is the rule for potential difference in parallel?
The potential difference across each branch is equal to the potential difference across the power supply.
What causes resistance?
Collisions between electrons and atoms/ions in the conducter.
What factors effect resistance?
- Thickness of the wire
- Temperature
- Length of wire
- Material of the wire
What is Ohm’s law?
The current flowing through a wire is directly proportional to the potential difference across it.
(If temperature is constant)
What does a diode do?
- Only lets current flow in one direction
- Very high resistance in one direction
How is the resistance of a thermistor effected when temperature increases?
The resistance will decrease.
How is the resistance of an LDR effected when light intensity increases?
The resistance will decrease.
What is the potential difference of mains electricity?
230V
What is the frequency of mains electricity?
50Hz
What are the names, colours, and positions of the three wires in a three pin plug.
Live: Brown - Bottom right (next to fuse)
Neutral: Blue - Bottom left
Earth: Yellow and green - Top
What are the pins in a plug made from and why?
Brass - it is strong and a good electrical conductor.
Is mains electricity AC or DC?
AC
How do the fuse and earth wire work if there is a fault in an applience?
- Current will flow along the earth wire
- The fuse will melt/blow cuttng of the supply
What is a circuit breaker?
An electromagnetic switch.
What does a step up transformer do and why?
- Increases the voltage and decreases the current
- Reduces energy lost through heating - increasing efficiency
What does a step down transformer do and why?
- Reduces the voltage and increases the current
- This is done to increase safety for consumers
Why is AC used for mains electricity?
- Easier to generate
- Transformers only work with AC
What is the equation for power in transformers?
P in = P out (assuming transformer is 100% efficient)
V x I = V x I
Which direction do electric field lines flow?
From positive to negative.
