Magnetic Field due to Circular Loop - UNSOLVED PRACTICE SET
Chapter: Magnetic Effects of Current | Topic: Magnetic Field due to Circular Loop
MAGNETIC FIELD DUE TO CIRCULAR LOOP - UNSOLVED PRACTICE SET
Topic: Magnetic Field due to Circular Loop
SECTION NAME
Q1. At the centre of a current-carrying circular loop, the magnetic field lines are:
- Circular, parallel to the plane of the loop
- Straight and perpendicular to the plane of the loop
- Zero
- Radial, pointing outward only
Q2. The magnetic field at the centre of a circular loop is directly proportional to:
- The radius of the loop
- The current and the number of turns
- The diameter squared
- The resistance of the wire
Q3. The magnetic field at the centre of a circular loop is inversely proportional to:
- The current
- The number of turns
- The radius of the loop
- The voltage applied
Q4. If the number of turns in a circular coil is doubled (keeping current and radius constant), the magnetic field at the centre:
- Halves
- Stays the same
- Doubles
- Becomes zero
Q5. If the radius of a circular current loop is doubled (keeping current and number of turns constant), the magnetic field at the centre:
- Doubles
- Halves
- Stays the same
- Quadruples
Q6. The magnetic field is strongest at which point of a current-carrying circular loop?
- At the edge of the loop only
- At the centre of the loop
- Outside the loop only
- Equally strong everywhere
Short Answer Questions
Q7. Describe the pattern of magnetic field lines for a current-carrying circular loop, both at the centre and near the wire itself.
Q8. How does the magnetic field at the centre of a circular loop depend on:
(a) the current through it, and
(b) the radius of the loop?
Q9. What is the effect of increasing the number of turns in a circular coil on the magnetic field at its centre? Why does this happen?
Q10. Explain why the magnetic field at the centre of a circular loop is stronger than the field due to a straight wire at the same distance from the wire.
Q11. A circular coil of radius 5 cm produces a certain magnetic field at its centre. If the radius is increased to 10 cm (current unchanged), what happens to the field? Explain your reasoning.
Q12. How can the direction of the magnetic field at the centre of a circular loop be determined? Relate this to the Right Hand Thumb Rule applied to a curved wire.
Long Answer Questions
Q13. Explain the magnetic field due to a current-carrying circular loop in detail. Your answer must cover:
(a) why bending a straight wire into a loop concentrates and strengthens the magnetic field at the centre,
(b) the factors affecting the magnetic field at the centre (current, radius, number of turns) and the nature of each relationship,
(c) how the Right Hand Thumb Rule is applied to a curved conductor to find the field direction,
(d) the field pattern both inside and outside the loop, and
(e) why this configuration is useful as a building block for electromagnets.
Q14. A student designs three circular coils for an experiment: Coil A โ 1 turn, radius 5 cm, current 2 A. Coil B โ 5 turns, radius 5 cm, current 2 A. Coil C โ 1 turn, radius 10 cm, current 2 A.
(a) Without calculating exact values, rank the three coils in order of magnetic field strength at their centres (strongest to weakest) and justify each ranking.
(b) If Coil B's current is doubled, how does its field compare to Coil A's original field?
(c) Suggest a combination of changes to Coil C (turns, current, radius) that would make its field equal to Coil B's original field.
Q15. Compare the magnetic field patterns of a straight current-carrying wire and a circular current-carrying loop.
(a) Describe the field pattern for each.
(b) Explain why the field lines are concentric circles around a straight wire but appear nearly straight and parallel at the centre of a circular loop (over a small region).
(c) Explain how multiple circular loops stacked together (a solenoid, which you will study next) would further enhance and shape this field.
(d) Give one real-life application that specifically uses a single circular current loop's magnetic field (e.g., in a simple galvanometer).
Numerical / Application-Based Problems
Q16. A circular coil with 50 turns and radius 4 cm carries a current of 0.5 A, producing a magnetic field B at its centre.
(a) If the current is increased to 2 A (turns and radius unchanged), express the new field in terms of B.
(b) If instead the number of turns is reduced to 25 (current and radius unchanged), express the new field in terms of B.
(c) If both changes in (a) and (b) are applied together, express the new field in terms of B.
Q17. Two circular coils, Coil P (20 turns, radius 3 cm, current 1 A) and Coil Q (10 turns, radius 6 cm, current 2 A), are compared.
(a) Using the proportionality B โ NI/r, calculate the ratio B_P : B_Q.
(b) Which coil produces a stronger field at its centre?
(c) If Coil Q's radius is halved (other values unchanged), recalculate the ratio B_P : B_Q.",3)
Q18. A school laboratory experiment uses a circular coil connected to a battery and a compass placed at its centre (a 'tangent galvanometer' setup).
(a) Explain why the compass at the centre is deflected when current flows.
(b) If the current is doubled, the deflection increases โ but does the deflection angle double too? (Recall: tan ฮธ โ B โ I, so deflection is NOT linear in current.)
(c) If the coil has 100 turns instead of 1 (same current and radius), by what factor does the field at the centre increase?
(d) Why are many turns used in real galvanometers rather than just one loop?