Force on a Current-Carrying Conductor - UNSOLVED PRACTICE SET

Q7. State the conditions under which a current-carrying conductor experiences a force when placed in a magnetic field.

Q8. How does the force on a current-carrying conductor depend on
(a) the strength of the magnetic field, and
(b) the magnitude of the current?

Q9. A straight wire carries current and is placed perpendicular to a uniform magnetic field. If the current is doubled and the magnetic field strength is also doubled, what happens to the force on the wire?

Q10. Explain why a current-carrying conductor placed parallel to the magnetic field experiences no force, while one placed perpendicular experiences maximum force.

Q11. Two parallel wires carry current in opposite directions. Will they attract or repel each other? (Hint: think about the magnetic field each creates and the force on the other due to that field.)

Q12. A simple experiment shows a wire jumping when current flows through it in a magnetic field (sometimes called the 'jumping wire' experiment). Explain what causes the wire to jump and in what direction it would move.

Q13. Explain the force experienced by a current-carrying conductor in a magnetic field in detail. Your answer must cover:
(a) the conditions necessary for the force to exist (current must have a component perpendicular to the field),
(b) how the force depends on current, magnetic field strength, length, and the angle between them,
(c) the special cases — force is zero when parallel (0°) and maximum when perpendicular (90°),
(d) what happens to the direction of force when current direction is reversed, and
(e) what happens when both current and field direction are reversed simultaneously.

Q14. Describe the 'jumping wire' experiment used to demonstrate the force on a current-carrying conductor in a magnetic field.
(a) Describe the setup: a flexible wire, a horseshoe magnet, and a battery/switch.
(b) What happens when the switch is closed and current flows?
(c) In which direction does the wire move, and what determines this direction?
(d) If the magnet is flipped (poles reversed) and the experiment repeated with the same current direction, how does the wire's motion change?
(e) If the current direction is reversed (magnet unchanged), how does the wire's motion change?
(f) What does this experiment tell us about converting electrical energy into mechanical motion?

Q15. Analyse the force between two parallel current-carrying conductors.
(a) When two parallel wires carry current in the SAME direction, do they attract or repel? Explain using the magnetic field produced by one wire and the force it exerts on the other.
(b) When the currents are in OPPOSITE directions, what happens?
(c) This phenomenon is actually used to define the SI unit of current (the Ampere) — briefly explain this historical significance.
(d) Give one practical situation where this force between current-carrying conductors must be considered by electrical engineers (e.g., in high-current busbars in power stations).

Q16. A straight conductor carrying current I is placed perpendicular to a magnetic field B and experiences a force F.
(a) If the current is tripled (B and length unchanged), express the new force in terms of F.
(b) If the conductor is now placed at 30° to the field instead of 90° (current and B unchanged), is the new force greater than, less than, or equal to F/2? (Use sin 30° = 0.5 and compare with sin 90° = 1.)
(c) If the conductor is placed parallel to the field (0°), what is the force?

Q17. A current-carrying horizontal wire is placed in a magnetic field pointing into the page. The current flows from left to right.
(a) Using Fleming's Left Hand Rule (which you will study formally in the next topic — but try using the simple relationship 'Force, Field, Current are mutually perpendicular' for now), reason about which direction (up, down, into page, out of page) the force on the wire would act.
(b) If the current direction is reversed (right to left), how does the force direction change?
(c) If the magnetic field direction is reversed (out of the page) with the original current direction, how does the force direction change compared to part (a)?

Q18. In a laboratory setup, a wire of length 10 cm carries a current of 2 A and is placed perpendicular to a magnetic field, experiencing a force of 0.04 N.
(a) If the length of the wire in the field is increased to 20 cm (current and field unchanged), what would the new force be?
(b) If the current is reduced to 1 A (length 10 cm, field unchanged), what would the new force be?
(c) If both the length is doubled AND the current is halved (compared to the original), what is the new force compared to the original 0.04 N?