P4 - Resistance Flashcards
1
Q
What is a variable resistor?
A
A variable resistor ( or rheostat ) is a resistor whose resistance can be changed.
2
Q
What are variable resistors useful for?
A
Variable resistors are useful for altering the current flowing through a circuit.
- Turn the resistance up, the current drops
- Turn the resistance down, the current goes up.
3
Q
What do older rheostats consist of?
A
Older versions are huge coils of wire with a slider on them.
4
Q
How do variable resistors work?
A
- As you move the slider, the length of wire that has a current flowing through it changes.
- Longer wires have more resistance, so have less current flowing them, this is because the longer the wire, the more material electric charge has to flow through, which increases resistance.
5
Q
How does thickness of a wire affect resistance?
A
- Thinner wires have more resistance, and so less current can flow through.
6
Q
Why do thinner wires increase resistance?
A
- The thinner the wire, the less space electric charge has to move through, which increases the resistance.
7
Q
What happens if you increase the voltage across a resistor?
A
If you increase the voltage across a resistor the current also increases.
8
Q
What is the formula for resistance?
A
Voltage/Current.
