Students can Download Science Chapter 14 Electric Current and its Effects Questions and Answers, Notes Pdf, KSEEB Solutions for Class 7 Science helps you to revise the complete Karnataka State Board Syllabus and to clear all their doubts, score well in final exams.
Karnataka State Syllabus Class 7 Science Chapter 14 Electric Current and its Effects
Class 7 Science Electric Current and its Effects Textbook Exercise Questions and Answers
Draw in your notebook the symbols to represent the following components of electrical circuits: connecting wires, switch in the ‘OFF’ position, bulb, cell, switch in the ‘ON’ position and battery.
Draw the circuit diagram to represent the circuit shown in the given figure.
The figure shows four cells fixed on aboard. Draw lines to indicate how you will connect their terminals with wires to make a battery of four cells.
The negative terminal of one cell is connected to the positive terminal of the next cell with the help of connecting wires to make a battery.
The bulb in the circuit shown in the figure does not glow. Can you identify the problem? Make necessary changes in the circuit to make the bulb glow.
The positive terminal of the electric cell is connected to the positive terminal of another cell. Hence, the bulb does not glow. To make the bulb glow; wre should connect the positive terminal of the cell to the negative terminal of the next cell.
Name any two effects of electric current,
The two effects of electric current are:
- Heating effect of electric current.
- Magnetic effect of electric current.
When the current is switched on through a wire, a compass needle kept nearby gets deflected from its North-South position, Explain,
The current flowing in the wire gives rise to a magnetic field around it which exerts a force on the compass needle (which itself is a tiny magnet) kept nearby and deflects it from its North-south position.
Will the compass needle show deflection when the switch in the circuit shown by the figure is closed?
No. There is no source of electric current in the circuit. Hence, the wire does not behave like a magnet and the compass needle will not show any deflection.
Fill in the blanks:
- The longer line in the symbol for a cell represents its _________________ terminal.
- The combination of two or more cells is called a _________________.
- When current is switched on In a room heater, it _________________.
- The safety device based on the heating effect of electric current is called a _________________.
- produces heat
Mark ‘T’ if the statement is true and ‘F’ if it is false:
(a) To make a battery of two cells, the negative terminal of one cell is connected to the negative terminal of the other cell, (T/F)
(b) When the electric current through the fuse exceeds a certain limit, the fuse-wire melts and breaks. (T/F)
(c) An electromagnet does not attract a piece of iron, (T/F)
(d) An electric bell has an electromagnet. (T/F)
Do you think an electromagnet can be used for separating plastic bags from a garbage heap? Explain.
No. Plastic bag is a non-magnetic material. An electromagnet attracts magnetic materials only. Hence, an electromagnet cannot be used for separating plastic bags ‘ from a garbage heap.
An electrician is carrying out some repairs in your house. He wants to replace a fuse by a piece of wire. Would you agree? Give reasons for ‘ your response.
No. The electrician cannot replace a fuse by a piece of wire because every wire cannot be used as a fuse wire. The fuse wire is made of special material which has a low melting point such that it could melt quickly and break when large amount of electric current is passed through it. Most of the wires have high melting points.
Zubeda made an electric circuit using a cell holder shown in figure, a switch and a bulb. When she puts the switch r in the ‘ON’ position, the bulb did not glow. Help Zubeda in identifying the possible defects in the circuit.
The reasons are:
(a) The two cells in the cell holder are not in contact with each other. The cell holder may not be tight enough to keep them in contact with each other. Then, the circuit will not be complete, and the current will not flow through the circuit. Hence, the bulb will not glow.
(b) The other reason could be the two cells are not connected properly. The positive terminal of one cell must be connected to the negative terminal of the other cell for the flow of electric current.
In the circuit shown in the figure:
(i) Would any of the bulb glow when the switch is in the ‘OFF’ position?
(ii) What will be the order in which the bulbs A, B, and C will glow when the switch is moved to the ‘ON’position?
(i) No, when the switch is in the ‘OFF’ position, the electric current will not flow through the circuit. Hence, none of the bulbs will glow.
(ii) When the switch is moved to the ‘ON’ position, all the three bulbs will glow simultaneously. This is because all are connected to the same battery, switch, and wire.