Charge and Current
Charge
All atoms contain charged particles of two types. Subatomic particle, with a negative charge and a negligible mass relative to protons and neutrons. have a negative charge and can be easily moved between atoms. Protons have a postive Property of matter that causes a force when near another charge. Charge comes in two forms, positive and negative. For example, a negative charge causes a repulsive force on a neighbouring negative charge. and cannot move between atoms.
When you use a cloth to rub an Material that does not allow charge or heat to pass through it easily. such as a balloon or a plastic ruler, electrons are rubbed from one to the other. A negatively charged object has gained electrons. A positively charged object has lost electrons.
If you bring two charged insulators close together, they will exert forces on each other. This is illustrate in the images below.
Two charged rods with the same charge
Two charged rods with different charge
Two rods where only one is charged
An electric Moving electric charges, eg electrons moving through a metal wire. is a movement of charge, so if the charge can move off an insulator, it forms a current.
Examples of charge producing a current
- If you rub your feet on some types of carpet, you will build up a charge. When you touch something else, the charge flows from your body and you feel the shock.
- Air masses moving past each other in clouds can build up charges. Sometimes there is enough energy to form long sparks. This is lightning.
In A material which allows charge to move easily through it., the electrons that carry the negative charges are free to move. The current in an electric A closed loop through which current moves - from a power source, through a series of components, and back into the power source. is caused by the movement of the charges through the conductors of the circuit.
The symbol for current is \(I\).
The unit that is used to measure current is the Unit of current, eg the current in the bulb is 4 amps or amperes (A). \((A)\).
The meter used to measure current is an A device used to measure electric current..
To measure the current of a circuit, we first need to break the circuit and insert the ammeter into it as shown below: