P6 Flashcards
What is the unit of voltage?
Volts.
What is the unit of current?
Amps.
What is the unit of resistance?
Ohms.
What is ohms law?
Voltage=Current x Resistance
v = I x R
How does a variable resistor work?
By changing the length of the wire.
How does a dimmer switch work?
It has a contact that moves around a circular coil of wire. The length of the wire changes, therefore resistance changes and current changes. This affects the brightness of the light.
What affects resistance? (3)
1) Its length. longer = more resistance
2) Its cross-sectional area. thin = more resistance
3) The material its made from.
What is current?
The flow of charge carriers e.g- electrons.
What happens when electrons flow in a wire and what does increased vibration mean?
When electrons flow in a wire they collide with the atoms in the wire making them vibrate more.
Increased vibration means-
- Increased number of collisions so increased resistance,
-Increased temperature of the wire.
How does a bulb glow?
electrons flow and collide with atoms making them vibrate more. Increased number of collisions so increased resistance. Increased temperature of wire. This causes the filament to get hot and so it glows.
What is an ohmic conductor?
An ohmic conductor is one that obeys ohms law. This means the voltage is directly proportional to current.
Give an example of an ohmic conductor
A fixed Resistor.
What is a non-ohmic conductor?
They do not obey ohms law.
Give an example of a non-ohmic conductor.
A filament lamp.
What are potential dividers?
They are used to produce a required voltage in a circuit. e.g- a fixed proportion of the supply voltage.
