1.
Name the SI unit of magnetic field strength (magnetic flux density).
2.
State the direction of magnetic field lines outside a bar magnet.
3.
What is the shape of magnetic field lines around a straight current-carrying conductor?
4.
Write one property of magnetic field lines that shows they never intersect each other.
5.
What happens to the magnetic field strength inside a solenoid when the number of turns is doubled, keeping everything else constant?
6.
Name the device used to protect household circuits from overloading.
7.
What is the frequency of AC supply in India?
8.
State Fleming's Left-Hand Rule in one sentence.
9.
What is the colour coding of the live wire in domestic circuits in India?
10.
What is an electromagnet?
11.
Draw a neat, labelled diagram showing the pattern of magnetic field lines around a bar magnet. State two properties of these lines.
12.
A current-carrying conductor is placed horizontally in the north-south direction. Using Fleming's Left-Hand Rule, determine the direction of the force on it if the current flows from south to north and the magnetic field acts vertically downward.
13.
Distinguish between AC and DC supply with one example of each.
14.
State two advantages of an electromagnet over a permanent magnet.
15.
What is a solenoid? How does it behave like a bar magnet?
16.
Why is it safer to use a three-pin plug than a two-pin plug for electrical appliances?
17.
What is a short circuit? State two causes of short circuit in domestic wiring.
18.
State two ways to increase the strength of the magnetic field produced by a current-carrying solenoid.
19.
Describe an activity to demonstrate that a current-carrying conductor placed in a magnetic field experiences a force. Mention the rule used to determine the direction of this force.
20.
With the help of a labelled diagram, explain how the magnetic field is produced by a current-carrying circular loop. State two factors on which the strength of this field at the centre depends.
21.
Compare the magnetic field inside a solenoid with that of a bar magnet. Why is a current-carrying solenoid equivalent to a bar magnet? (Explain using the right-hand thumb rule.)
22.
A proton moves horizontally eastward with velocity $v$ inside a uniform magnetic field directed vertically upward (out of the page).
- Using Fleming's Left-Hand Rule, determine the direction of force on the proton.
- What happens if an electron moves in the same direction in the same field?
- If the proton moves parallel to the field, what is the force on it?
23.
Explain the domestic electric circuit in India. Why are the live, neutral, and earth wires colour-coded differently? Draw a schematic diagram showing a bulb and a switch connected properly.
24.
Define overloading in electrical circuits. What are its two main causes? Explain how a fuse prevents damage due to overloading.
25.
State the right-hand thumb rule. Using it, determine the direction of the magnetic field:
- Above a horizontal conductor in which current flows from west to east.
- At the centre of a circular loop in which current flows anticlockwise when viewed from the front.
26.
(a) With a neat labelled diagram, describe the construction and working of an electric bell. How does the electromagnet principle work in it?
(b) If the resistance of the electromagnet coil is $5\ \Omega$ and a potential difference of $12\ \text{V}$ is applied, calculate the current flowing through the coil and the power dissipated. (3 + 2)
27.
(a) Draw the pattern of magnetic field lines for a current-carrying solenoid. How does it compare with a bar magnet? Explain any two factors that affect the strength of the magnetic field inside a solenoid.
(b) A solenoid of length 40 cm has 200 turns. If the current is 2 A, write an expression for the magnetic field inside and describe how it changes if the core is replaced by soft iron. (3 + 2)
28.
Riya's family recently got their house rewired. The electrician installed separate circuits for lighting and heavy appliances. He explained that the live wire carries current at high potential, the neutral wire completes the circuit, and the earth wire provides a safety path to the ground. He also replaced old fuses with MCBs (Miniature Circuit Breakers) in the distribution board.
- Why are separate circuits used for lighting and heavy appliances? (1)
- What is the function of the earth wire? Which appliances must be earthed and why? (1)
- State one advantage of an MCB over a wire fuse. (1)
- If the total power used in the house is 3300 W at 220 V, calculate the current drawn and suggest the minimum fuse rating. (1)
29.
Electromagnets are widely used in scrap yards to lift heavy iron and steel objects. Unlike permanent magnets, their magnetic strength can be controlled. A large electromagnet consists of a soft iron core wound with many turns of insulated copper wire. When current flows, it becomes a powerful magnet; when current is switched off, the magnetism disappears, allowing the load to be released precisely.
- Why is soft iron preferred over steel for the core of an electromagnet? (1)
- State two ways to increase the lifting power of the electromagnet. (1)
- Give one other practical application of an electromagnet. (1)
- If the same coil is used with a steel core instead of soft iron, what disadvantage would occur in the scrap yard operation? (1)
30.
During a school experiment, students placed a small aluminium rod (AB) horizontally across two conducting rails inside a horseshoe magnet. When a current was passed through the circuit, the rod moved. By changing the direction of the current or flipping the magnet, they could control the direction of the rod's movement. The teacher noted this is the principle behind the working of a galvanometer, which is used to detect small currents.
- Name the rule used to find the direction of force on the rod. (1)
- What three quantities determine the magnitude of the force on a current-carrying conductor in a magnetic field? (1)
- If current in the rod flows from A to B (east to west) and the magnetic field points vertically upward, determine the direction of force on the rod. (1)
- Why does a galvanometer use this principle, and not electromagnetic induction? (1)
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