NCERT Exemplar Problems Class 6 Science – Electricity and Circuits
Choose from the options (a), (b), (c) and (d) given below the figure which shows the correct direction of current.
(b) Current always starts from positive terminal and end at negative terminal of the battery. This is conventional direction of flow of current in a circuit.
Choose the incorrect statement.
(a) A switch is the source of electric current in a circuit
(b) A switch helps to complete or break the circuit
(c) A switch helps us to use electricity as per our requirement
(d) When the switch is open, there is an air gap between its terminals
(a) A switch cannot be a source of electric current in the circuit. Electric cell is a source of electricity in the circuit. Other options are the functions of a switch.
In an electric bulb, light is produced due to the glowing of
(a) the glass case of the bulb (b) the thin filament
(c) the thick wires supporting the filament (d) gases inside glass case of the bulb
(b) In an electric bulb, its thin filament glows and gives off light and heat.
In the following arrangement shown in figure, the bulb will not glow if the ends A and B are connected with
(a) a steel spoon (b) a metal clip (c) a plastic clip (d) a copper wire
(c) Since, a plastic clip is an insulator, so current will not pass through it and bulb will not glow in this case. However, a steel spoon, a metal clip and a copper wire are conductors of electricity.
In the circuit shown in figure, when the switch is moved to ON position, then
(a) the bulb A will glow first (b) the bulb B will glow first
(c) the bulb C will glow first (d) all bulbs will glow together
(d) All the bulbs will glow together because current will reach simultaneously to all the bulbs, when the switch is moved to ON position.
Filament of a torch bulb is
(a) a metal case
(b) metal tip at the centre of the base
(c) two thick wires
(d) a thin wire
(d) Filament of a torch bulb is a thin wire which gives off light. It is fixed to two thicker wires which provides support to it.
One of these thick wires is connected to the metal case at the base of the bulb and the other thick wire is connected to the metal tip at the centre of the base.
Paheli is running short of connecting wires. To complete an electric circuit, she may use a
(a) glass bangle (b) thick thread
(c) rubber pipe (d) steel spoon
(d) Since, a steel spoon is a conductor of electricity therefore, current will pass through it. So, Paheli can use a steel spoon to complete the circuit.
Very Short Answer Type Questions
In which of the following circuits A, B and C given in figure, the cell will be used up very rapidly?
The cell will be used up rapidly in A because all the current will discharge through the wire very rapidly as no appliance is connected between the positive and negative terminals of the cell.
Figure shows a bulb with its different parts marked as 1, 2, 3, 4 and 5. Which of them label the terminals of the bulb?
1 -> Glass covering 2 -> Filament
3 —> Terminal 4 -> Terminal
5 -> Base wires (supporting filament)
As from the question, labels 3 and 4 are the terminals of the bulb.
Short Answer Type Questions
You are provided with a bulb, a cell, a switch and some connecting wires. Draw a diagram to show the connections between them to make the bulb glow.
The complete circuit diagram so that the bulb glows is given below:
Will the bulb glow in the circuit shown in figure? Explain.
As in the given circuit diagram, it seems that the switch is open, i.e. there is an air gap between the connecting wires, so the circuit is not complete and therefore, the bulb will not glow.
An electric bulb is connected to a cell through a switch as shown in figure. When the switch is brought in ON position, the bulb does not glow. What could be the possible reasons for it? Mention any two of them.
The possible reasons so that even at switch ON position the bulb is not glowing are:
(i) The cell may be discharged.
(ii) The bulb may be fused.
(iii) The wire may be broken from inside.
(iv) The connections may be loose.
A torch requires 3 cells. Show the arrangement of the cells with a diagram inside the torch so that the bulb glows.
The arrangement of bulb should be such that the positive terminal of a battery touches the base of the bulb. When switched ON, the bulb will glow.
When the chemicals in the electric cell are used up, the electric cell stops producing electricity. The electric cell is then replaced with a new one. In case of rechargeable batteries (such as the type used in mobile phones, cameras and inverters), they are used again and again. How?
A rechargeable battery has such chemicals which on after usage can be restored, by passing a suitable current in the opposite direction to the rechargeable battery, so that it can be used again and again.
Paheli connected two bulbs to a cell as shown in figure.
She found that filament of bulb B is broken. Will the bulb A glow in this circuit? Give reason.
No, the bulb A will not glow in the circuit because the filament of the bulb 8 is broken and the current will not pass through it, i.e. the circuit is broken or incomplete. Therefore, the current will not flow in the whole circuit.
Why do bulbs have two terminals?
Bulb has two terminals to connect the filament with the terminals of a cell or a battery so that the current can pass through the filament.
Which of the following arrangement A, B, C and D given in figure should not be set up? Explain why.
Arrangement A should not be set up because in this arrangement cell will be used up very rapidly as no appliance is connected between the two terminals of the cell.
A fused bulb does not glow. Why?
A fused bulb does not glow because in a fused bulb, the filament is broken and the circuit is incomplete. Therefore, the current does not flow through it.
Paheli wanted to glow a torch bulb using a cell. She could not get connecting wires, instead, she got two strips of aluminium foil. Will she succeed? Explain how.
Yes, she will succeed. Aluminium foils can act as connecting wires because aluminium is
a conductor of electricity, it will complete the circuit and therefore, the bulb will glow.
Long Answer Type Questions
Boojho has a cell and a single piece of connecting wire. Without cutting the wire in two, will he be able to make the bulb glow? Explain with the help of a circuit diagram.
Yes, this can be done by arranging the circuit as given below:
In this arrangement, one terminal of the bulb should be connected directly to the positive (say) terminal of the cell and the other terminal of the bulb should be connected to the negative terminal of the cell using the given piece of connecting wire.
Figures A and B show a bulb connected to a cell in two different ways.
(a) What will be the direction of the current through the bulb in both the cases (Q to P or P to Q)?
(b) Will the bulb glow in both the cases?
(c) Does the brightness of the glowing bulb depend on the direction of current through it?
(a) The direction of current will be from 0 to P in A and direction of current will be from PtoQ in B. This is because the direction of current is always from positive terminal to negative terminal of the cell or battery. This is the conventional direction of flow of current in the circuit.
(b) Yes, the bulb will glow in both the cases because for the bulb to glow, we just need to complete the circuit.
(c) No, the brightness of the bulb never depends upon the direction of current passing through it.
Think of six activities which use electric current. Also name the devices used to perform the activity.
The name of the devices and their activity are as given:
A torch is not functioning, though contact points in the torch are in working condition. What can be the possible reasons for this? Mention any three.
The possible reasons for not functioning of torch are:
(i) The torch bulb may be fused.
(ii) The cells may be discharged.
(iii) The connecting wires may be broken up.
(iv) The cells may not be placed in the correct order.
(v) The switch is faulty.