P4 - Electric Circuits

How does some insulating materials get charged?

When they are rubbed together

What are two occurences when objects transfer electrons whilst charged?

- insulating materials that become positively charged when rubbed lose electrons.
- insulating materials that become negatively charged when rubbed gain electrons.

What pair of charges repel and attract?

Like charges repel and unlike charges attract.

What is a non-contact force?

The force between two charged objects.

What is a battery?

two or more cells connected together

The size of the electric current is the...

rate of flow of charge

What is Ohm's law?

current through a resistor at a constant temperature is directly proportional to the potential difference across the resistor

What happens if you reverse the potential difference across a resistor?

It also reverses the current through it

What factor can affect a filament lamp's resistance

If temperature increases then filament lamp's resistance increases

What is the resistance for a diode in both directions?

forward - resistance low
reverse - resistance high

If a thermistor's temperature increases...

the resistance decreases

A LDR's resistance decreases if the...

light intensity increases

For components in series:

The current is the same in each component
the total potential difference is shared between components
Adding their resistances gives the total resistance

For cells in series, the total potential difference =

The sum of their indvididual potential differences

What happens if you increase resistors in a series circuit?

The total resistance increases

For parallel circuits:

The total current is the sum of all the currents through the separate components
The potential difference across each component is the same

The bigger the resistance of a component...

The smaller the current that will pass through that component

Adding more resistors in parallel...

decreases the total resistance as the total current is increased and the potential difference stays the same.