Electricity Flashcards
What is current?
The flow of electric charge around the circuit. Unit= Amps (A)
In a single closed loop the current is…?
The same everywhere
What is the potential difference?
(Voltage) is the driving force that pushes the charge round
What is resistance?
Anything in the circuit that slows the flow down. Unit= ohms
What links resistance and current?
The greater the resistance across a component, the smaller the current that flows through it.
What is the equation that links charge current and time?
Charge = current x time
What is charge measured in?
Coulombs
What is the equation that links voltage current and resistance
Voltage= current x resistance
What do conductors have?
A low resistance
What do insulators have?
A high resistance
What is an IV characteristic
Refers to a graph which shows how the current flowing through a component changes as the potential difference across it increased
Thermistor Resistance
1) Resistance decreases as temperature increases
2) Is a temperature dependent resistor
3) In hot conditions, the resistance drops
4) In cool conditions, resistance goes up
.LDR
1) A resistor that is dependent on the intensity of light
2) In bright light, the resistance falls
3) In darkness, the resistance is highest
In a parallel circuit, what does adding a resistor do?
Reduces the total resistance
AC=
Main supply
DC=
Battery supply
Factors of AC supplies
The current is constantly changing direction. they are produced by alternating pd in which the positive and negative ends keep alternating
What is the UK main supply
ac 230V, frequency is 50 cycles per second or 50Hz
Direct current factors
current that is always flowing in the same direction. Created by a direct pd
Why do wires have a outer plastic coating?
Double insulating. Casing is an insualtor so no current conducts to user
Neutral Wire
Blue, completes the circuit, 0V
Live wire
brown, alternates between a positive and negative voltage (230V)
Earth Wire
Green/Yellow takes current to ‘earth’ if there is a fault.
What happens if you touch the live wire?
A large pd is produced across your body and a current flows through you. This causes an electric shock
Why are wires made out of copper?
Becasue good conductor and flexible
What are pins made out of?
Brass because good conductor
What is the equation linking power resistance and voltage
power = current x voltage
What effect does a current through a wire have on the wire
If the current is too much, the wire will melt.
What is the equation linking energy charge and voltage
Energy = charge x voltage
What is the equation linking power current and resistance
Power = current squared x resistance
What is the national grid?
Distributes electricity via transformers and power lines to home
Step up transformer?
increases voltage and is found between power station and power lines
Step down transformer?
Decreases voltage and is found between power lines and homes.
