P5

Electric Current is a flow of charge.

Metal conductors have many charges (electrons) that are free to move. Electric Current is the movement of these free electrons. Insulators do not conduct electricity. This is because they have very few charges that are free to move.

Charging an Insulator;

When you rub 2 different insulating materials against each other they become electrically charged. This only works for insulated objects. When materials are rubbed against each other;

• Negatively charged particles called electrons move from one material to the other
• The material that loses electrons becomes positively charged and the material that gains electrons becomes negatively charged.
• Both materials gain an equal amount of charge, but the charges are opposite.

Resistance is measured in ohms. This can be calculated in different type of circuit. 

Battery Voltage;

The size of a current in a circuit depends on the voltage of the battery and the resistance of the components in the circuit. Voltage can be thought of as the 'push' it exerts on charges in the circuit. A bigger voltage means a bigger 'push', resulting in a larger current.

Resistance;

The bigger the resistance, the smaller the current.

Resistance (Ω) = Voltage (V) / Current (A)

Potential Differencemeans the same as voltage, can use a voltmeter to measure the potential difference across a component in a circuit.

Series; 

3 components are connected to batteries, the same current flows through each component, potential differences across the components add up to the potential difference across the battery.

Parallel;

3 components are connected in parallel to the battery, the current at the battery on each side is equal to the sum of the currents through the components, the current is largest through the component with the smallest resistance.

A voltage is produced when a magnet moves into a coil of wire. This principle is used in generators to produce electricity - either a coil of wire rotates in a magnetic field, or a magnet rotates in a coil of wire.

Transformers are used to increase or decrease the voltage of alternating current supplies.

Electromagnetic Induction;

A voltage is produced when a magnet is moving into a coil of wire. This process is called electromagnetic induction. If you join up the ends of the coil to make a circuit, current flows. You can induce a voltage in the opposite direction by; moving the magnet out of the coil or moving the other pole of the magnet into the coil.

Generators make electricity by electromagnetic induction. In a generator, a magnet or electromagnet turns near a coil of wire. This induces a voltage across the ends of the coil. The direction of this voltage changes each time the magnet rotates. You can increase the size of the induced voltage by; turning the magnet faster, adding more turns to the coil, making the magnetic field stronger, putting an iron core inside the coil

Transformers; 

A transformer is an electrical device that changes the voltage. A transformer changes a high-voltage supply into a low-voltage one or vice versa

A transformer that increases the voltage is called a step-up transformer and a transformer that decreases the voltage is called a step-down transformer. Step-down transformers are used in mains adapters and rechargers for mobile phones and CD players. 

Electric motors transfer electrical energy into kinetic energy, using magnets and coils of wire. 

If a current is flowing through a wire or coil, the wire or coil can exert a force on a nearby permanent magnet or another current-carrying coil or wire nearby

For a current-carrying wire in a magnetic field, if the magnet's lines of force are at 90 degrees on the wire, the wire experiences a force at 90 degrees to both the current direction and lines of force of the field, and if the magnet's lines of force are parallel to the wire, the wire experiences no force

Motors are used in computer hard disk drives, DVD players, and electric motor vehicles.