🔌 Series & Parallel Circuits

1. A battery is the energy source of an electric circuit.
2. The larger the number of batteries connected in an electric circuit in series, the larger the amount of electric current flowing through the electric circuit.
3. An increase in the number of batteries in series causes an increase in the brightness of the bulb.

4. If too many batteries are used, too much electric current will flow through the bulb and the metal filament of the bulb will overheat and melt/fuse.
5. A gap will form in the filament of the bulb. As a result, the bulb will become fused and will not light up.

1. The larger the number of bulbs connected in an electric circuit in series, the smaller the amount of electric current flowing through the electric circuit.
2. An increase in the number of bulbs in series causes a decrease in the brightness of the bulbs.

1. When two bulbs are used in an electric circuit, they can be connected in two different arrangements — series or parallel.
2. The two bulbs arranged in parallel light up more brightly than the two bulbs arranged in series.

3. In a series arrangement, the bulbs are connected one after another in a single loop.
4. Adding a bulb in series to a circuit causes the original bulb to be less bright.

5. In a parallel arrangement, each bulb is connected on its own separate branch.
6. Adding a bulb in parallel to a circuit causes the original bulb to remain the same brightness.

Arrangement	Brightness (2 bulbs vs 1)
Series	Both bulbs are less bright
Parallel	Both bulbs have the same brightness

1. The magnetic strength of an electromagnet depends on the following factors:

2. The greater the amount of current passing through the wire (e.g., by adding more batteries in series), the greater the magnetic strength of the electromagnet.

3. The greater the number of coils of wire around the rod, the greater the magnetic strength of the electromagnet.

An electric bell uses an electromagnet to produce a continuous ringing sound. Here is the 3-step cycle:

1. When the switch is pressed, a closed circuit is formed.
2. Electric current flows through the circuit, causing the electromagnets to be magnetised.
3. The electromagnets then attract the iron strip, causing the hammer to hit the gong and make a sound.

4. At the same time, the metal contact no longer touches the iron strip, creating an open circuit.
5. Electric current stops flowing through the electromagnets, causing them to lose their magnetism and stop attracting the iron strip.
6. The iron strip will then return to its original position.

7. A closed circuit is formed again, causing the hammer to hit the gong once more.
8. The repetition of this process causes the bell to ring continuously as long as the switch is pressed.

1. Electricity is produced in power stations and passed through underground cables to reach our homes.
2. Electricity enables electrical appliances to work.
3. To produce electricity in power stations, fossil fuels such as gas, coal and oil are burnt.
4. Singapore has to spend money to buy coal and be reliant on other countries. If we waste electricity, we are wasting money.

5. The burning of fossil fuels is harmful to the environment because air pollutants and greenhouse gases are produced during this process.
6. Air pollutants may cause acid rain while greenhouse gases may cause global warming.
7. Fossil fuels are limited/finite/non-renewable natural resources and will not last long.

8. The more electricity we use, the more fossil fuels we have to burn and the faster they run out, so we should conserve electricity.
9. To conserve electricity, we can use a fan instead of an air conditioner.
10. We should also switch off the electrical appliances when we are not using them.

1. We must handle electricity with care because it can be very dangerous/hazardous.
2. Electricity can cause a person to suffer an electric shock and fires to break out.
3. Lives may be lost and properties may be destroyed by electric fires.

4. To prevent electric fires, we should not overload a socket by putting too many plugs into it.
5. We should also not use a plug or an appliance with exposed/damaged/frayed wires.