Electricity Introduction - Topic 2 Flashcards
State two conditions needed for a current to flow.
1) A complete circuit
2) A source of potential difference (e.g. a cell, battery)
Define ‘electrical current’
The rate of flow of charge.
In a circuit, which particle moves to cause a flow of charge?
Electrons
State the equation linking charge and current
Q = I × t
Charge flow (C) = current (A) x time (S
State the units for charge
Coulombs (C)
How does the potential difference of a source affect the current in a circuit?
The higher the potential difference of the source (cell, or battery) the higher the current in the circuit.
How does the amount of resistance in a circuit affect current?
The higher the resistance, the lower the current (for a given potential difference).
What causes resistance in a wire?
Collisions of electrons with ions in the wire
How does increasing the length of a wire affect its resistance?
· More ions in the wire
· So more collisions of electrons with ions
· So more resistance
State one factor, other than length, that affects the resistance of a wire.
Thickness of the wire
(Thinner the wire, the greater the resistance)
Write Ohm’s law as an equation
V = I × R
What are the units of potential difference?
Volts (V)
What are the units of current?
Amperes (A)
What are the units of resistance?
Ohms (Ω)
Which piece of equipment is used to measure current in a circuit?
Ammeter
