MYP Physics Electric Circuits Notes

How Does Electric Current Flow Through Circuits?

1. An electric circuit is a complete, closed path that allows electric charge to move.
2. Understanding circuits means keeping track of three linked ideas:
   1. Charge: the "stuff" that moves (in metals, this is mainly electrons)
   2. Current: how fast charge passes a point
   3. Potential difference (voltage): the energy difference that pushes charge around the circuit
3. Electric current can only flow when the circuit forms a closed loop from the energy source, through the components, and back to the source.
4. If there is a break anywhere in the pathway, charges cannot complete the loop and the circuit stops working.
5. Circuits are used to transfer electrical energy from a source to devices such as lamps, motors, or heaters.

Open and closed circuits

1. A closed circuit provides a continuous loop, so charges can flow without interruption.
2. An open circuit has a break in the path, which prevents current from flowing.
3. Switches are commonly used to deliberately open or close a circuit.

What Parts Are Needed To Make A Circuit Work?

1. To transfer electrical energy, a circuit must contain certain essential components.
2. Each component has a specific role, and removing any one of them prevents the circuit from working properly.

Cells and Batteries

1. A cell provides energy to charges in the circuit.
2. The cell pushes charges around the circuit by providing voltage.
3. A battery is made of two or more cells connected together.
4. Increasing the number of cells increases the energy transferred to charges.

Conducting Wires

1. Wires connect all components to form a complete loop.
2. Wires are made of metals because metals allow charges to move easily.
3. Wires are designed to have very low resistance, so little energy is lost in them.

Switches

1. A switch controls whether a circuit is open or closed.
2. Opening a switch breaks the circuit and stops current.
3. Closing a switch completes the circuit and allows current to flow.

Electrical Devices (Loads)

1. Devices in a circuit are often called loads.
2. Loads transfer electrical energy into other forms:
   1. Lamps → light and heat
   2. Motors → movement