Electricity Flashcards
What is the equation that links Energy,Charge and Voltage
Energy (J) = Charge (C) * Voltage (V)
What is the equation that links Energy,Power and Time
Energy (J) = Power (W) * Time (S)
What is the Equation that links Power,Voltage and current
Power (W) = Voltage (V) * Current (A)
What is the equation that links Power,Current and Resistance
Power (W) = Current² (A) * Resistance (Ω)
What is the equation that links Charge,Current and Time
Charge (C) = Current (A) * Time (s)
What is the equation that links Voltage,Current and Resistance
Voltage (V) = Current (A) * Resistance (Ω)
What is the equation for Efficiency
Efficiency = Useful Power
——————— * 100
Total Input Power
What is current
rate of flow of charge
What is unit for Charge
Coulombs (C)
Define Voltage
Potential Difference- Energy transferred per unit charge
What is voltage always proportional to in series
Voltage is always proportional to the current when resistance is contsant (temp. remains constant)
What stays the same in series
Same current goes through the cell and resistors in circuit. I Cell. IR = IR2
What is shared between resistors in series
Voltage is shared between resistors. Vcell = VR1 + VR2
How is current calculated in series
Current = Total Voltage / Total Resistance
How is proportionate share of voltage calculated in series
Resistance of compound/total resistance = proportionate share of voltage
What stays the same in parallel circuits
Voltage stays the same. Vcell = V1 + V2
What happens to current in parallel circuits
Current splits in parallel circuits so I0 = I1 + i2
How is current calculated
I1 = Vcell/R1
What is the relationship between resistance and light in a LDR
Resistance decreases as light intensity increases, non-linear
What is the relationship between resistance and temperature in a thermistor
Resistance of a thermistor decreases, as temp. increases. Non-Linear
What is the quality of an ohmic conductor
Current is directly proportional to the voltage running through it
Why is current and voltage not proportional in a non-ohmic conductor
As voltage inc., current inc. , so temp. inc causing resistance to inc.
What is the forward direction of a diode and led
——->—- (right is forward). it doesn’t work in the reversal direction
What is direct current
current in one direction only
what is alternating current
current repeatedly reverses its direction. UK mains is this
In which direction does current flow
Positive to negative (anticlockwise)
What is the frequency of the UK Mains circuit
50Hz
What is the peak voltage of the Uk Mains
325V
What is the average Voltage of the Uk mains
230V
What is the time period of the Uk mains
0.02 s
Name three factors that affect the resistance of metals (at a constant temp.)
- Type of Metal
- Length of Metal (Longer Wire,higher resistance)
- Thickness of Metal (thinner wire,higher resistance)
What material are electrical cables made out of
Copper
What are the wires encased in
plastic as it is an electrical insulator
What 3 wires do the cable contain and what colours are each
- Earth = Green/Yellow
- Live=Brown
- Neutral=Blue
What is the purpose of the Live Wire
It contains the AC Current
What is the purpose of the Neutral Wire
It stays at zero and completes the circuit
What is the purpose of the Earth Wire
It connects the appliance case to the earth so if an accident occurs a very large current overloads to the earth and blows the fuse
What is the purpose of a fuse
If the current exceeds the limit the fuse melts and stops the circuit
what can only move in static electricity
only electrons
What can electrons do in conductors
electrons can move across the object giving negative charge (induced charge)
What can electrons do in insulators
electrons can move to one side of the atom
How can objects be charged
They can be charged by friction
