P2- Current Electricity Flashcards
Opposites..
Attract.
Objects with the same electric charge..
Repel each other.
How can we calculate current?
I= Q/t
I= current in amperes (A).
Q= charge in coulombs (C).
t= time in seconds (s).
How does an insulator become negatively charged?
It gains electrons.
What circuit symbol is this?
Switch (open)
The switch enables the current to be switched on or off.
What circuit symbol is this?
Switch (closed)
The switch enables the current to be switched on or off.
What circuit symbol is this?
Cell
A cell is needed to push electrons around a complete circuit.
What circuit symbol is this?
Battery
A battery consists of two or more cells.
What circuit symbol is this?
Ammeter
An ammeter measures electric current.
What circuit symbol is this?
Voltmeter
A voltmeter measures potential difference (voltage).
What circuit symbol is this?
Motor
What circuit symbol is this?
Lamp
Emits light when a current passes through it.
What circuit symbol is this?
Fuse
Designed to melt if current going through it is greater than a certain amount➡️Breaks circuit
What circuit symbol is this?
Fixed resistor
Limits the current in a circuit.
What circuit symbol is this?
Variable resistor
Allows current to be varied.
What circuit symbol is this?
Light dependent resistor
What circuit symbol is this?
Diode
Allows current through in one direction only.
What circuit symbol is this?
Light-emitting diode
Emits light when a current passes through it.
What circuit symbol is this?
Heater
Transfers electrical energy to heat the surroundings.
How can we calculate potential difference (voltage)?
V=W/Q
V= Potential difference in volts (V).
W= work done in joules (J).
Q= charge in coulombs (C).
How can resistance be calculated?
R=V/I
R= resistance in ohms (Ω).
V= potential difference in volts (V).
I= current in amps (A).
Where should voltmeters always be placed in relation with the measured component?
In parallel.
What is resistance?
Resistance is the opposition to current flow.
What is the unit of resistance?
Ohms.
Where should ammeters be placed in relation to the measured component?
In series.
What is Ohm’s law?
Ohm’s law states that the current through a resistor at constant temperature is directly proportional to the potential difference across the resistor.
What does this graph show and why?
A current-potential difference graph for a filament light bulb.
The line is a curve because the wire gets hotter for larger currents.
What does this graph show and why?
A current-potential difference graph for a diode.
The current only flows in one direction so in reverse direction the diode has very high resistance so the current is zero.
What does this graph show?
A resistance-temperature graph for a thermistor.
As the temperature increases, the resistance decreases.
What does this graph show?
A resistance-light intensity graph for a light-dependent resistor.
As light intensity increases, resistance decreases.
What happens in a series circuit if one component stops working?
No current flows.
This is because in a series circuit, they are all connected one after the other and there is only one route for the charge to flow.
How could you find the total potential difference in a series circuit?
Add all the individual potential differences.
How could you find the total resistance in a series circuit?
Add all the individual resistances.
What happens in a parallel circuit if one component stops working?
Current can’t flow to that one component, but can flow to all the other components.
This is because each component is connected across the supply.
How could you find the total current in a parallel circuit?
Add the individual currents.
How could you find the total voltage in a parallel circuit?
In a parallel circuit the potential difference is the same across each component.
How does current depend on resistance in a parallel circuit?
The bigger the resistance of a component, the smaller the current is.
What circle symbol is this?
Thermistor.
Why is it important that ammeters have very low resistance?
So the ammeter reduces the current as little as possible.
The resistance of the bulb increases as the potential difference across the bulb increases. Why?
Temperature of bulb increases.
