topic 2 - electricity Flashcards
unit for current
amperes (A)
unit for charge
coulombs (C)
unit for resistance
ohms (Ω)
unit for time
seconds (s)
unit for potential difference
volt (V)
unit for power
watt (W)
how do fuses help protect
Stop the flow of current by melting if the current is too high, protecting sensitive components and people because if the components function at too higher temperature it can cause a fire.
how do circuit breakers help protect
break the circuit if current is too high.
how do insulation and double insulation help protect
prevent people from touching exposed wires and getting shocks.
how does earthing help protect
provides a low resistance path to the earth so if some one does come into contact with a current instead of flowing through them to the earth giving them a shock it flows through the earthing wire.
what can resistance cause a transfer of
electrical energy to heat energy. Some components are designed to have a high resistance to make sure this happens e.g. electrical heaters that have lots of resistors to ensure a high resistance so a lot of heat is produced
relationship between power, current and voltage
power = current x voltage
P = I x V
energy transferred, current, voltage and time
energy transferred = current x voltage x time
E = VIt
what is alternating current
AC is constantly changing magnitude and direction. AC is how mains electricity is produced from turbines.
what is direct current
DC is constant. And is produced from a battery and used in some sensitive components like in computing.
3 advantages of parallel circuits
- Components (e.g. bulbs) may be switched on/off independently.
- If one component breaks, current can still flow through the other parts of the circuit.
- Bulbs maintain a similar brightness.
2 advantages of series circuits
- Fewer wires, cheaper and easier to assemble.
- Uses less power
what is the relationship between voltage and resistance
as voltage increases, resistance also increases
qualitative effect of changing resistance on the current in a circuit
Since V = IR, as you increase the resistance in a circuit, the current will decrease.
qualitative variation of resistance of light-dependent resistors (LDRs) with illumination
as illumination increases, resistance decreases
qualitative variation of resistance of thermistors with temperature
as temperature increases, resistance decreases
how can LED’s be used to show current in a circuit
A lamp can be added to a circuit to check for a current. If current is flowing, the lamp will light up.
relationship between voltage, resistance and current
voltage = resistance x current
V = IR
what is current
rate flow of charge
relationship between charge, current and time
charge = current x time
Q = It
what are electrons in a solid metal conductor like
Electrons are negatively charged and free to flow in a metal so carry charge
why is current conserved at a junction in a circuit
At a junction current ‘splits’ to take both paths.
It comes back together when the paths meet again.
what is the voltage across two components connected in parallel
the voltage is the same
relationship between voltage, energy transferred per unit passed and charge
voltage = energy transferred/charge
V = E/Q
