We began by studying how fluids flow, because there are many analogies between this and electrical circuits. We defined the flow rate of a fluid to be the amount of fluid that is delivered, divided by how long it took to deliver it. Fluids flow downhill because this lowers their gravitational energy: a height difference between two ends of a pipe gives rise to a pressure difference that makes the fluid go. The flow rate is also affected by the size of the pipe or tube carrying the fluid. The electrical equivalents to these are the electrical current (measured in amperes); the current flows because there is a voltage difference; and the size of the current is affected by the resistance of the wire.

As an interesting special case we studied siphons. Here some fluid is moving upwards but this is allowed because elsewhere fluid is flowing downwards, and the gravitational energy of the whole system is decreasing.

The electrical quantity that is analogous to the flow rate of a fluid is the electrical current, which is measured in Amperes. The analog of pressure is voltage. Electrical current stays inside conductors (such as wires). In order for an electrical device to work there has to be a path for the current: a circuit. Some electrical devices only work when the current flows the right way.

A circuit delivers energy to a circuit component. The power (energy per unit time) is the product of the current through the device and the voltage difference across it (Watts = Volts x Amperes).

A high dam provides water pressure. When water flows through the turbine, energy is converted into mechanical form (motion). The amount of power released depends on the pressure and the flow rate	spacer	A battery provides electrical potential (voltage). When current flows through the motor, energy is converted into mechanical form (motion). The amount of power released depends on the voltage and the current

In some respects electricity is safer than other ways to deliver energy, but we must be respectful of it, since we can't see or hear or smell an electrical hazard. The current required to deliver a lethal shock is very small. The basic rule is to avoid becoming part of an electrical circuit that would send current through the chest area.

We have studied several electrical components:

• Wires. The electrical current stays inside the wires, and make it possible for us to determine where the current goes, and what the circuit does.
• Incandescent light bulbs. These are a way to turn electrical energy into light.
• Switches. By connecting and disconnecting parts of a circuit, we can affect which parts are working.
• Batteries. These are devices for converting chemical energy into electrical energy.
• Buzzer. This is one of several ways to make sound using an electrical signal.
• Motor. This is a device for turning electrical energy into mechanical energy.

pictures of these things