Exercises: Basic electric circuits

Match each component of a circuit with its function. Components: generator, conducting wire, receiver, and switch. Functions: drives the charges, carries current from one point to another, makes use of electrical energy, and opens or closes the path of the current.

Explain in your own words the difference between an open circuit and a closed circuit. Look at the two setups in the diagram:

In which of the two does the bulb light up? Why?

What does a switch do in a circuit? Relate it to open and closed circuits: what state does each switch position leave the circuit in?

In circuit diagrams, circuit components are drawn using standardised symbols, which are the same worldwide: a cell is represented by two parallel lines, one long and thin and the other short and thick; a bulb, a circle with a cross inside; a switch, a raised line. Here are the three symbols:

Draw the circuit diagram of a circuit with a cell, a switch and a bulb in your notebook.

You can do it on paper and send a photo with your answer.

What is an electrical receiver? Give three examples of electrical receivers in your home and state what the electrical energy is transformed into in each one (for example, a bulb transforms it into light).

You want to set up a circuit to light a bulb using a cell. Make a list of all the materials you need and explain what each one is used for.

Inside a torch there is a cell, a bulb, a switch and a metal spring connecting everything, as shown in the diagram.

1. a) Which component drives the charges?
2. b) Which component makes use of the energy?
3. c) What does the switch do when turning on the torch?

State whether each component in this list is a generator or a receiver: the battery of a remote control, the motor of a fan, the battery of an electric scooter, a doorbell buzzer and a bulb.

Two bulbs are connected one after the other, in series, to the same cell, as shown in the diagram.

1. a) If one of the bulbs blows, what happens to the other one?
2. b) Explain this by considering the path the current follows.

Now the two bulbs are connected in parallel: each one has its own path for the current from the cell, as shown in the diagram.

1. a) If one blows, does the other one stay lit?
2. b) How do you think the lights in your home are connected, in series or in parallel? Give reasons for your answer.

In a single-path circuit there is a cell, a switch and a bulb. If we change the order and place the bulb first and then the switch, will it still work in the same way? Explain why the order of components does not matter when there is only one path.

Aoife sets up her circuit with a cell, wires and a bulb, but it does not light up. State three possible causes of the fault and explain how she would test each one to find the problem.

With a $1.5\ \text{V}$ cell, the bulb in the setup shines dimly. The diagram shows the setup with two cells placed one after the other:

1. a) What voltage will two $1.5\ \text{V}$ cells supply when placed one after the other?
2. b) What will happen to the brightness of the bulb when switching to two cells?

A corridor has two bulbs connected in series. Where should the switch be placed to turn off both at the same time: next to the first one, next to the second one, or does it not matter where on the path it is? Justify your answer.

Draw a circuit diagram in your notebook, using standardised symbols, of a circuit with a cell, a switch, a bulb and a buzzer, all on the same path. If the switch is left open, which components work? Explain why.

You can do it on paper and send a photo with your answer.

Two bulbs are connected in parallel and we want to turn off both at the same time with a single switch. Where would you place it: in one of the branches or in the main path, before the circuit splits? Draw the circuit diagram in your notebook and justify your answer.

You can do it on paper and send a photo with your answer.

Using the same cell, we set up two circuits: one with two bulbs in series and another with two bulbs in parallel.

1. a) In which of the two do the bulbs shine brighter? Give reasons for your answer by considering how difficult the path is for the current.
2. b) What happens in each circuit if a bulb blows?
3. c) Which of the two setups would you choose for home lighting? Why?

A set of Christmas lights has twenty bulbs connected in series.

1. a) Why do all the bulbs go out when just one blows?
2. b) How should they be connected so that this does not happen?
3. c) Propose a practical method to locate the blown bulb among the twenty.

You want to set up two light bulbs in your bedroom that can be turned on and off separately using a single battery.

1. a) How would you connect them, in series or in parallel? Why?
2. b) How many switches do you need and at which point in the circuit?
3. c) Draw the diagram in your notebook.

You can do it on paper and send a photo with your answer.

We add light bulbs in series to the same battery: first one, then two, and then three.

1. a) What happens to the brightness of each bulb as more are added?
2. b) Explain the cause by considering the difficulty the current faces in passing through.
3. c) Predict what would happen to the brightness if we added them in parallel instead of in series.

If we connect the two terminals of a battery directly with a wire, without any component, as shown in the figure, a short circuit occurs: the battery and the wire get very hot, and the battery gets damaged.

1. a) Explain what happens to the current when it finds nothing to use the energy.
2. b) Why can a short circuit in a home installation be dangerous?

A doorbell only rings while the button at the front door is kept pressed.

1. a) What type of control component is that button, and what does it do to the circuit when pressed and released?
2. b) Describe the complete circuit of the doorbell when a visitor presses and releases it.
3. c) Are the button and the doorbell in series or in parallel? Give reasons for your answer.

Hugo sets up his circuit as follows: a wire goes from one terminal of the battery to the bulb, and another wire goes from the bulb back to the same terminal of the battery, as shown in the figure.

1. a) Will the bulb light up?
2. b) What mistake has he made?
3. c) Explain how the circuit should be arranged so that the current completes a full loop.

The light inside the fridge turns on when opening the door and turns off when closing it.

1. a) What circuit component does the door activate without us noticing?
2. b) Explain what happens to the light circuit when opening and closing the door.
3. c) Considering household energy consumption, why is it important that the light turns off automatically?