Static Electricity, Force Fields, Current, Resistance, Electromagnets, Forces, Speed, Turning forces and pivots Flashcards
Static Electricity
A positive or negative charge on an insulation material is caused when rubbing transfers electrons from one material to another.
Resistance
The resistance of a component is a way of saying how easy or difficult it is for an electric current
to flow through it.
The formula for calculating resistance
resistance= voltage/current
Electromagnets
A bar magnet is a permanent magnet because
it is always magnetic. It is only
magnetic while the current is flowing.
You can make an electromagnet stronger by:
- increasing the number of coils of wire
- increasing the size of the current (by increasing the voltage)
- using an iron core.
What is the Motor effect?
If a wire carrying a current crosses a magnetic
field, the wire will experience a force.
What does an electric motor consist of?
An electric motor consists of a coil of wire in a
magnetic field. When there is a current in the
coil, there is a force on each side of the coil that
makes it turn.
The speed of the motor (or the force it provides)
can be increased by:
- increasing the size of the current
- increasing the strength of the magnetic field
- increasing the number of turns of wire on
the coil.
Formula for speed
speed = distance/time
Units for speed
km/h or m/s or mph
Gradients
The gradient of a line on a graph is a measure of how steep the line is.
Formula for gradient
gradient = vertical change (distance moved)/horizontal change (time taken)
Levers and Moments
Forces can be used to turn objects around pivots. A pivot is also known as a fulcrum.
Simple Machines
A lever is an example of a simple machine. Ramps and pulleys are simple machines that act as force multipliers.
