Magnetic Effects of Electric Current Class 10 Important Questions: This chapter clearly explains how an electric current generates a magnetic field, how this field behaves around straight conductors, coils, and solenoids, and why these patterns are important in real-life applications.
Concepts like electromagnets, electric motors, fuses, and household circuits help students understand the practical magnetic effect of electric current important questions included in the chapter.
Magnetic Effect of Electric Current Class 10 Important Questions Answers
These magnetic effect of electric current Class 10 Important Questions help students understand field patterns, rules for direction of current and force, and applications such as electromagnets and motors. Practice them to build clarity and score well in board exams.
Multiple Choice Question [1 Mark]
Class 10 Science Chapter 12 Magnetic effects of current: Magnetic field, field lines, field due to a current-carrying conductor, field due to a current-carrying coil or solenoid; force on current-carrying conductor, Fleming's Left Hand Rule, direct current.
Alternating current: frequency of AC, advantage of AC over DC, and domestic electric circuits.
1. Magnetic field lines are always
(A) Straight lines
(B) Zig-zag lines
(C) Hyperbola
(D) Closed loops
Ans (D)
3. An electron is moving in the north direction. It experiences a force in the vertically upward direction. The magnetic field at that region is towards
(A) East
(B) West
(C) North
(D) South
Ans. (A)
4. A vertical wire carrying a current in the upward direction is placed in a horizontal magnetic field directed towards east. The wire will experience a force directed towards
(A) East
(B) West
(C) North
(D) South
Ans. (C)
5. How many times does an alternating current (AC) with frequency 50 Hz changes its direction?
(A) 25
(B) 75
(C) 50
(D) 100
Ans. (D)
6. Choose the correct magnetic field pattern due to current through a long straight conductor.
7. Which of the following devices should be used for protecting the circuits due to short-circuiting or overloading of the circuits?
(A) Switch
(B) Socket
(C) Fuse
(D) Resistance
Ans. (C)
8. When a current carrying conductor is placed in a uniform magnetic field it experiences a force. The direction of the force is given by
(A) Fleming's left-hand rule
(B) Fleming's right-hand rule
(C) Right-hand thumb rule
(D) Left-hand thumb rule
Ans. (C)
9. An alpha particle enters a uniform magnetic field as shown. The direction of force experienced by the alpha particle is:
10. Switches are connected to
(A) live wire.
(B) neutral wire.
(C) earth wire.
(D) Anyone of these
Ans. (A)
11. Assertion: The magnetic field is stronger at a point which is nearer to the conductor and goes on decreasing on moving away from the conductor.
Reason: The magnetic field B produced by a straight current carrying wire is inversely proportional to the distance from the wire.
(A) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).
(B) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
(C) Assertion (A) is true but reason (R) is false.
(D) Assertion (A) is false but reason (R) is true.
Ans. (A)
12. Assertion: Magnetic field lines do not intersect.
Reason: Magnetic field lines are closed curves
(A) Both 'A' and 'R' are true and 'R' is correct explanation of the Assertion.
(B) Both 'A' and 'R' are true but 'R' is not correct explanation of the Assertion
(C) 'A' is true but 'R' is false.
(D) 'A' is false but 'R' is true.
Ans. (B)
13. Assertion (A): The magnetic field inside a solenoid is uniform
Reason (R): The magnetic field lines inside a solenoid are parallel.
(A) Both 'A' and 'R' are true and 'R' is correct explanation of the Assertion.
(B) Both 'A' and 'R' are true but 'R' is not correct explanation of the Assertion
(C) 'A' is true but 'R' is false.
(D) 'A' is false but 'R' is true
Ans. (A)
14. Assertion: The magnetic field produced by a current carrying solenoid is independent of its length and cross-sectional area.
Reason: The magnetic field inside the solenoid is uniform.
(A) Both 'A' and 'R' are true and 'R' is correct explanation of the Assertion.
(B) Both 'A' and 'R' are true but 'R' is not correct explanation of the Assertion
(C) 'A' is true but 'R' is false.
(D) 'A' is false but 'R' is true
Ans. (B)
15. Assertion: In Fleming's Left Hand Rule, the direction of magnetic field, force and current are mutually perpendicular.
Reason: Fleming's Left hand Rule is applied to measure the induced current.
(A) Both 'A' and 'R' are true and 'R' is correct explanation of the Assertion.
(B) Both 'A' and 'R' are true but 'R' is not correct explanation of the Assertion.
(C) 'A' is true but 'R' is false.
(D) 'A' is false but 'R' is true.
Ans. (C)
Very Short Answer Type Question [1 Mark]
16. When is the force experienced by a current carrying straight conductor placed in a uniform magnetic field
(i) Maximum:
(ii) Minimum?
Sol.
(i) The force experienced by a current-carrying straight conductor is maximum when the conductor is placed perpendicular to the direction of magnetic field.
(ii) The force experienced by a current-carrying straight conductor is minimum when the conductor is placed along the direction of magnetic field whether parallel or antiparallel.
17. (a) Distinguish between the terms 'overloading' and 'short-circuiting' as used in domestic circuits.
(b) Why are the coils of electric toasters made of any alloy rather than a pure metal?
Sol.
(a) Short circuiting – When neutral and live wire come in direct contact.
Overloading – When too many appliances are connected to a single socket drawing much more current or power than permissible.
(b) Resistivity of an alloy is higher than its constituent metal and alloys do not oxidize as easily as constituent metal at high temperature. That is why the coils of electric toasters are made of an alloy rather than a pure metal.
18. (i) Why is an alternating current (A.C.) considered to be advantageous over direct current (D.C.) for the long distance transmission of electric power?
(ii) How is the type of current used in household supply different from the one given by a battery of dry cells?
(iii) How does an electric fuse prevent the electric circuit and the appliances from a possible damage due to short circuiting or overloading.
Sol.
(i) Alternating current (A.C.) can be transmitted over long distance with a very low loss of energy in comparison to Direct current (D.C.).
(ii) The type of current used in household supply is alternating current which continuously vary in direction and magnitude whereas the current given by the battery of dry cells is direct current which is of constant magnitude and direction.
(iii) A fuse is a safety device having a short length of a thin wire made of tin-lead alloy which has a lower melting point. This wire melts and breaks the circuit if the current exceeds the safe value. This saves costly electric appliances and buildings from damage.
19. (a) In a pattern of magnetic field lines due to bar magnet, how can the regions of relative strength be identified?
(b) Compare the strength of magnetic field near the poles and the middle of a bar magnet.
Sol.
(a) The closeness of lines measures the relative strength of magnetic field.
(b) The strength of magnetic field is highest near the poles whereas minimum in the middle of bar magnet.
20. (a) Fuse acts like a watchman in an electric circuit. Justify this statement.
(b) Mention the usual current rating of the fuse wire in the line to
(i) lights and fans
(ii) appliance of 2 kW or more power.
Sol.
(a) When an unduly high electric current flows through the circuit, the fuse wire melts due to joule heating effect and breaks the circuit. Hence, it keeps an eye on the amount of current flowing and also stops the current if exceeds the maximum value. So, fuse acts like a watchman in an electric circuit.
(b) (i) A fuse of rating 5A is usually used for lights and fans.
(ii) A fuse of rating 15A is usually used for appliance of 2 kW or more power.
21. What is the difference between a direct current and an alternating current? What is the frequency of AC in India?
Sol.
| DC | AC |
| The current flows in a single direction | Direction of current changes periodically (every 1/100 second in India) |
| Cannot be transmitted over long distances. | Can be transmitted over long distances without much loss in energy. |
| Source of DC – cell, battery | Source of AC – AC generator |
Frequency of AC in India: 50 Hz
22. What is a solenoid? Draw a sketch of the pattern of field lines of the magnetic field through and around a current carrying solenoid.
Sol.
A solenoid is a long coil (shaped like a cylinder) containing a large number of close turns of insulated copper wire.
23. (a) What is an electromagnet? List any two uses.
(b) Draw a labelled diagram to show how an electromagnet is made.
(c) State the purpose of soft iron core used in making an electromagnet.
(d) List two ways of increasing the strength of an electromagnet if the material of the electromagnet is fixed.
Sol.
(a) An electromagnet is a temporary magnet made from a piece of soft iron when current flows in the coil wound around it.
Uses of electromagnet:
(i) For removing pieces of iron from wounds
(ii) For lifting and transporting the large masses of iron scrap, grinders, plates etc.
(c) If a core of soft iron is placed inside a solenoid, the magnetic field strength inside the solenoid is greatly increased.
(d)
(i) By increasing the number of turns of winding
(ii) By increasing the current
24. An electric kettle rated as 1200 W at 220 V and a toaster rated at 1000 W at 220 V are both connected in parallel to a source of 220 V. If the fuse connected to the source blows when the current exceeds 9.0 A, can both appliances be used at the same time? Illustrate your answer with calculations.
25. A domestic lighting circuit has a fuse of 5 A. If the mains supply is at 230 V, calculate the maximum number of 36 W tube-lights that can be safely used in this circuit.
Sol. Let the maximum number of tube-lights be y.
Power of y tube-lights, P = 36y
V = 230 ~ V, I = 5
We know that
P=V I
36y = 230 × 5
Y = 31.94
So, the number of tube-lights that can be safely
used is 31.
26. What is the function of an earth wire? Why is it necessary to earth the metallic bodies of electrical appliances?
Sol. The main function of the earth wire is to conduct the excess or the leaking current from the electrical appliance to the ground.
It is necessary to earth metallic bodies because it protects us from getting an electric shock by transferring the current to the earth.
Because, if the metallic bodies of electric appliances are earthed, then the current would flow directly into the earth rather than entering our body. Hence, we won't get an electric shock
27. Read the passage below and answer the questions.
A magnetic field is described by drawing the magnetic field lines. When a small north magnetic pole is placed in the magnetic field created by a magnet, it will experience a force. And if the north pole is free, it will move under the influence of magnetic field. The path traced by a north magnetic pole free to move under the influence of a magnetic field is called a magnetic field line.
Since the direction of magnetic field line is the direction of force on a north pole, so the magnetic field lines always begin from the N-pole of a magnet and end on the S-pole of the magnet. Inside the magnet, however, the direction of magnetic field lines is from the S-pole of the magnet to the N-pole of the magnet. Thus, the magnetic field lines are closed curves.
When a small compass is moved along a magnetic field line, the compass needle always sets itself along the line tangential to it. So, a line drawn from the south pole of the compass needle to its north pole indicates the direction of the magnetic field at that point.
(a) State any two properties of magnetic field lines.
Sol.
-
Magnetic lines of force start from the North Pole and end at the South Pole.
-
They are continuous through the body of magnet.
-
Two magnetic lines of force cannot intersect each other.
-
The relative strength of the magnetic field is shown by the degree of closeness of the field lines.
(b) Why two magnetic field lines never intersect each other?
Sol. If magnetic field lines intersect each other, then at the intersection point there will be two directions of the same field which is not possible. Hence the field lines do not cross or intersect each other.
(c) State the rule for finding the direction of magnetic field associated with a current carrying conductor.
Sol. Right hand thumb rule determines the direction of magnetic field associated with a current carrying conductor. It states that imagine that you are holding a current-carrying straight conductor in your right hand such that the thumb points towards the direction of current. Then your fingers will wrap around the conductor in the direction of the field lines of the magnetic field.
28. Read the following passage and answer the questions.
A student was asked to perform an experiment to study the force on a current carrying conductor in a magnetic field. He took a small aluminium rod AB, a strong horse-shoe magnet, some connecting wires, a battery and a switch and connected them as shown. He observed that on passing current, the rod gets displaced. On reversing the direction of current, the direction of displacement also gets reversed. On the basis of your understanding of this phenomenon, answer the following questions:
(i) State the condition under which the displacement of the rod is largest for the same magnitude of current flowing through it.
Sol. When magnet will be perpendicular to the current carrying conductor then displacement of the rod will be maximum.
(ii) State the rule that determines the direction of the force on the conductor AB.
Sol. Fleming's left hand rule gives the direction of force experienced by current carrying conductor placed in an external magnetic field. According to Fleming's left hand rule the thumb, First finger and second finger are hold mutually perpendicular to each other. The thumb represent the direction of force on the conductor.
(iii) If the U shaped magnet is held vertically and the aluminium rod is suspended horizontally with its end B towards due north, then on passing current through the rod from B to A as shown, in which direction will the rod be displaced?
Sol. The direction will the rod displaced towards west to east.