2 ELECTRICITY Flashcards
Unit for current
Ampere (A)
Unit for charge
Coulomb (C)
Unit for energy
Joule (J)
Unit for resistance
Ohm ( X )
Unit for time
Second (s)
Unit for voltage
(V)
Unit for power
Watt (W)
Dangers of electricity
- Electric Shocks
- Electrical fires
- Damage appliances
How does insulation protect the user?
- Plastic coating covers the wires, so no current flows, as plastic is an insulator
- If someone touches it, they don’t get shocked and prevents short circuits
How does double insulation protect the user?
- Appliances with a plastic case and insulated wires
- If a fault occurs inside, there is no orute for the current to take, so no risk of shock
How do fuses protect the user?
- A thin wire in a ceramic case, when current flows through, it heats up
- When current is too high, the wire melts and is ‘blown’
- Breaks the curcuit, os the user is safe, a nd appliance undamaged
How does an earth wire protect user?
- Appliances in metal cases are earthed, and the earth wires connect to the case
- If the live wire cones loose and touches the case, you are at risk of shock
- Earth wire provides a lower resistance route for current, so current flows thorugh the earth wire, not the user
- As resistance is low, a high current flows which breaks the fuse
Advantages of circuit breakers over fuses
- Can be reset - use magnets not wires
- Act quicker than fuses
Charge equation
Charge = current x time
Charge symbol equation
Q = It
What is potential differance
Voltage
Voltage equation
Voltage = Current x Resistance
Voltage symbol equation
V = IR
What is a volt
Joule per coulomb (J/C)
Define current
The rate of flow of charge
Define voltage
The energy transferred per unit charge passed
Energy equation (charge)
Energy = charge x time
Energy equation (triple)
Energy = current x time x voltage
Energy equation (charge) symbol
E = Qt
Energy equation (triple) symbol
E = IVt
Direction of A.C
Constantly changing
Voltage of A.C
Mains electricity - 230V
Direction of D.C
Current only flows one way (conventional)
Voltage of D.C
Low voltage - Batteries and cells
Power equation
Power = Current x Voltage
Power equation symbol
P = IV