Current Electricity Flashcards
What is current and its formula, symbol and unit?
The amount of charges flowing per unit time. Current = Charge ÷ Time. Unit: A (Ampere). Symbol: I
What is the formula for charge and its unit?
Q = ne
n is the number of electrons and e is the charge of 1 electron.
Unit: C (coulomb)
What is the charge on 1 electron?
1.6 X 10^-19 C
What does an ammeter measure?
It is used to measure current
What scale on an ammeter will you use to measure 4A?
A 0-5 scale because it is more accurate
What does a milliammeter do?
It is used to measure very small current
What is electromotive force?
The work done per unit charge moved around a complete electric circuit
What is the formula of e.m.f?
E.M.F = Workdone ÷ Charge
What is e.m.f measured in?
J/C or V
What is the advantage of using cells in parallel?
Lamps glow more brightly
What is the potential difference and the formula, symbol and unit?
It is the electrical work done to carry unit charge between 2 points in an electrical circuit.
V = Electrical energy/Work done ÷ charge
unit: v (volt)
What does a voltmeter measure?
The voltmeter measures voltage
How are voltmeters and ammeters connected to a battery?
The positive terminal of the voltmeter/ammeter is always connected to the positive terminal of the battery
In what circuit is a voltmeter connected?
Parallel
In what circuit is an ammeter connected?
Series
What is the formula for resistance? Unit?
R = V ÷ I
unit: ohm
What is ohm’s law?
It states that the current passing through a conductor is directly proportional to the voltage difference across the conductor provided that the temperature is kept constant
What is the formula for ohms law?
V = IR
What happens to the resistance when temperature is increased?
The resistance increases
What happens to the resistance when voltage increases?
When voltage increases, temperature increases thus resistance increases
How does a light dependant resistor work?
When light increases the resistance will decrease
How do you calculate the net resistance in a series circuit?
net resistance = R1 + R2
How do you calculate the net resistance in a parallel circuit?
(1÷R1 + 1÷R2)-1
What is the advantage of cells arranged in series?
What is the resistance of the wire proportional to?
Its length
(The longer the wire the higher its resistance)
What is the resistance of a wire inversely proportional to?
The wires area
(The thicker the wire the lower its resistance)
