Electric current Flashcards
Define electric current
Rate of flow of charge
Define conventional current
From positive to negative
Define electron flow
From negative to positive
What is the formula for current, using current in coulombs and time?
I = Q/t
Current (A) = Current (C) / Time (s)
Define potential difference
Voltage
The energy used up
Define EMF
Electro-motive force
The energy supplied
What is the formula for voltage, using work and charge?
V = W/Q
Potential difference = Work (J) / Charge (C)
What is the formula for resistance, using voltage and current?
R = V/I
Resistance = Voltage (V) / Current (A)
What are the 3 factors affecting resistance?
Thickness of wire
Length of wire
Temperature
Define cell
DC only
Can run out (temporary)
Define power supply
DC / AC
Not a cell
Doesn’t run out (permanent)
Define variable resistor
Has the ability to change its resistance
Define thermistor
Reacts to temperature - Changes its resistance according to temperature
Define light-dependant resistor
Day-night switch. Relies on light to change its resistance
Define diode
Changes AC current to DC current
Define fuse
To stop current from going into the circuit that causes damage
Describe a series circuit
Current has only 1 path
Voltage must add up to total EMF
Total Resistance = R1 + R2 + …
Current stays the same at all points in a circuit
Describe a parallel circuit
Current has more than 1 path
Voltage is the same in the branches
The current adds up in the branches i.e. Total current = A1 + A2 + …
Total Resistance = 1/R1 + 1/R2 + …
