Topic Two - Electricity Flashcards
What is the current in a single closed loop circuit?
The current has the same value everywhere.
What is potential difference?
The driving force that pushes the charge around.
What is resistance?
Anything in the curcuit that slows the flow down.
What is the unit of current?
amps.
What is the unit of potential difference?
Volts.
What is the unit of resistance?
Ohms.
What happens if their is a greater resistance in the component?
The grater the resistance across a component the smaller the current that flows through it.
What is charge measured in?
Coulombs.
What is time measured in for the charge equation?
Seconds.
What happens to the reistance of an ohmic conductor? ( wire or resistor ).
It doesnt change with the current if it is at a constant temperature the current through a ohmic conductor is directly proportional to the potential difference across it.
What happenes to the resistance of a filament lamp?
The electric chanrge of a filament lamp transfers some energy to the thermal energy store of the filament which heats up. Resistance increases with temperature so as the current increases the lamp heats up more and the resistance increases.
What happens to the resistance in diodes?
It depends on the direction of the current. If the flow of the current is reversed the resistance will be very high.
What must the ammeter be in the resistance practical?
In series with whatever yor investigating.
Where must the volmeter be in the resistance practical?
In parallel around what your not investigating.
What is the method for the investigating resistance practical?
- attach a crocodile clip to the wire level with 0cm on the ruler.
- attach a second crocodile clip to the wire at a different length along the ruler and write down the length between the clips.
- close the switch and record the current and potential difference across it.
- open the second crocodile clip and move it further along the wire then close the switch measure the distance between, current and potential difference.
- repeat this for diferent lengths of the test wire.
- use the measurements to calculate the resistance for each length of wire.
What is the relationship between length and resistance?
Directly proportional.
Why may the graph for the resistance practical not go through the origin?
The first clip may not be attached at exactly zero so all readings are abit out it is a systematic error.
What does the ammeter measure?
Current.
What does the voltmeter measure?
Potential difference.
What type of wire will give you the best results for the resistance practical?
A thin wire and make sure its straight.
What might effect the resistance in the resistance practical?
The wire may heat up so leave the switch open between readings to let the circuit cool down.