83 free MCQs on Moving Charges and Magnetism, each with its own worked answer and explanation. Magnetic force on moving charges and currents, the Biot-Savart law, Ampere's law, and the cyclotron - how electric currents create and respond to magnetic fields.
Take the timed Moving Charges and Magnetism chapterwise test →83 practice questions on Moving Charges and Magnetism, sorted Easy → Hard. Try each one first, then open its answer page for the worked explanation. Want the full theory first? Read the Moving Charges and Magnetism notes.
The magnetic field around a long straight current-carrying wire forms concentric circles, with direction given by the right-hand rule (point thumb along I, fingers curl in the direction of B).
Q1.
A straight wire carrying a current of 5 A is placed along the direction of a uniform magnetic field of 0.4 T. The force per unit length on the wire is:
Q2.
The magnetic force acting on an electric charge that is at rest in a magnetic field is:
Q3.
In a moving-coil galvanometer the deflection is proportional to the current because the restoring couple of the suspension is proportional to:
Q4.
One tesla is equivalent to:
Q5.
Fleming's left-hand rule gives the direction of:
Q6.
The magnetic field in the region outside a closely wound toroid is:
Q8.
Force on a charge q moving with velocity v in magnetic field B:
Q9.
A current-carrying conductor placed in a magnetic field experiences a force. This is called:
Q10.
Direction of magnetic field inside a solenoid:
Q11.
A moving coil galvanometer uses a:
Q12.
In an electric motor, electrical energy converts to:
Q13.
Oersted's experiment showed that:
Q14.
A charge moving parallel to a magnetic field:
Q15.
A long, straight current-carrying wire produces a magnetic field whose field lines form:
Q16.
Which device uses the principle that a current-carrying coil placed in a magnetic field experiences a torque, to measure small electric currents?
Q17.
A moving electric charge produces:
Q18.
The SI unit of magnetic field (magnetic flux density) is the:
Q19.
The magnetic force on a charge moving parallel to a magnetic field is:
Q20.
The direction of the force on a current-carrying conductor in a magnetic field is given by:
Q21.
A current-carrying conductor placed in a magnetic field experiences a:
Q22.
The magnetic field lines around a straight current-carrying wire form:
Q23.
The instrument used to detect and measure small electric currents is the:
Q24.
The magnetic force on a stationary charge placed in a magnetic field is:
Q25.
A current-carrying solenoid behaves like a:
Q27.
A circular loop of radius 0.1 m carries a current of 2 A. Its magnetic dipole moment is:
Q28.
An electron moving at 2 × 10<sup>6</sup> m/s enters a field of 0.5 T perpendicularly. The force on it is (e = 1.6 × 10<sup>-19</sup> C):
Q29.
A wire of length 0.5 m carrying 4 A lies perpendicular to a 0.2 T field. The force on the wire is:
Q30.
The magnetic field at the centre of a circular coil of 50 turns, radius 0.05 m, carrying 2 A is (μ<sub>0</sub> = 4π × 10<sup>-7</sup>):
Q31.
A proton and a deuteron (mass twice the proton) enter a magnetic field perpendicularly with the same momentum. The ratio of their circular radii r<sub>p</sub> : r<sub>d</sub> is:
Q32.
A proton moves in a 0.5 T magnetic field. Its cyclotron frequency is (e = 1.6 × 10<sup>-19</sup>, m<sub>p</sub> = 1.67 × 10<sup>-27</sup>):
Q33.
A proton moves perpendicular to B=0.1 T field at 10<sup>6</sup> m/s. Radius of circular path (m<sub>p</sub> = 1.67 x 10<sup>-27</sup> kg, e = 1.6 x 10<sup>-19</sup> C):
Q34.
A long straight wire carries 10 A. Magnetic field at 0.1 m from wire (mu<sub>0</sub> = 4pi x 10<sup>-7</sup>):
Q35.
For a solenoid of n turns per unit length carrying current I, internal field is:
Q36.
Two parallel wires carry currents in same direction. They:
Q37.
In a cyclotron, the frequency of applied alternating voltage (cyclotron frequency) is:
Q38.
A charged particle in a uniform magnetic field moves in a:
Q39.
Magnetic force on a current-carrying conductor in a field B is F = BIL sin(theta). Force is zero when:
Q40.
A current-carrying circular loop is placed in a uniform external magnetic field with its magnetic moment initially anti-parallel to the field. The loop is in:
Q41.
A moving coil galvanometer can be converted into a voltmeter of higher range by:
Q42.
A charged particle moves undeflected through a region containing both an electric field E and a perpendicular magnetic field B, with the fields oriented so the forces oppose each other. The speed of the particle must be:
Q43.
The magnetic force F = qvB sinθ is maximum when the angle θ is:
Q44.
The magnetic field at the centre of a circular loop of radius R carrying current I is:
Q45.
The magnetic field due to a long straight wire at a perpendicular distance r is:
Q46.
A charged particle entering a uniform magnetic field perpendicular to it follows a path that is:
Q47.
The radius of the circular path of a charge q of mass m moving at speed v in a field B is:
Q48.
Two long parallel wires carrying currents in the same direction:
Q49.
Ampère’s circuital law relates the magnetic field around a loop to the ___ enclosed by it:
Q50.
When a charged particle moves through a magnetic field, its ___ remains unchanged:
Q51.
The magnetic field inside a long solenoid with n turns per unit length carrying current I is:
Q52.
A moving-coil galvanometer works on the principle that a current-carrying coil in a magnetic field experiences a:
Q53.
A charged particle moving perpendicular to a magnetic field completes one revolution in time T. If the field strength is tripled, the new period of revolution is:
Q54.
A charged particle moves at 30° to a uniform magnetic field in a helical path. If the field strength is doubled, the pitch of the helix becomes:
Q55.
A galvanometer of resistance 20 Ω shows full-scale deflection at 5 mA. To convert it into an ammeter reading up to 5 A, the shunt required is about:
Q56.
A Hall probe measures charge carrier sign in a semiconductor. If holes are majority carriers, voltage measured is:
Q57.
Magnetic vector potential A is related to B by:
Q58.
Magnetic field at center of a current loop (radius R, current I):
Q59.
A proton and an alpha particle enter the same perpendicular magnetic field with same speed. Ratio of radii r<sub>p</sub> : r<sub>alpha</sub>:
Q60.
A velocity selector uses perpendicular E and B fields. Particles pass straight when:
Q61.
A circular coil of radius R carrying current I is placed with its plane perpendicular to a uniform magnetic field B. If the coil is now turned so its plane becomes parallel to B, the torque on the coil changes from its initial value to:
Q62.
A toroid has a mean radius of 0.2 m and 500 turns, carrying a current of 4 A. The magnetic field inside the toroid (along the mean circumference) is approximately:
Q63.
A current-carrying wire is bent into a semicircular arc of radius R, and current I flows through it. The magnetic field at the centre of the arc due to this semicircular section is:
Q64.
An electron moving with speed v enters a region of uniform magnetic field B at an angle θ (not 90°) to the field, where 0° < θ < 90°. The path traced by the electron is:
Q65.
A long straight wire carrying current I<sub>1</sub> = 5 A is placed parallel to another wire carrying current I<sub>2</sub> = 10 A, 0.05 m apart, with currents in opposite directions. The force per unit length between the wires is approximately, and its nature is:
Q66.
The time period T = 2πm/qB of a charged particle in a magnetic field is independent of the particle’s:
Q67.
Two parallel wires 1 m apart each carry 1 A. The force per unit length between them is:
Q68.
A proton and an electron enter the same magnetic field with equal speeds. The radius of the proton’s path is ___ the electron’s:
Q69.
In a cyclotron, the frequency of the alternating voltage is set equal to the ___ frequency of the particle:
Q70.
The magnetic force acting on a moving charge can change its ___ but never its speed:
Q71.
A plane current loop of area A carrying current I has a magnetic moment equal to:
Q72.
The torque on a current loop of magnetic moment m in a uniform field B is:
Q73.
To convert a galvanometer into an ammeter, a small resistance is connected:
Q74.
To convert a galvanometer into a voltmeter, a large resistance is connected:
Q75.
The work done by the magnetic force on a moving charged particle is always:
Q76.
A charge of 1.6×10⁻¹⁹ C moves at 10⁶ m/s perpendicular to a magnetic field of 0.1 T. The magnetic force on it is:
Q77.
A charged particle moves in a circle in a magnetic field. If its speed is doubled (field unchanged), the radius of its path:
Q78.
A long solenoid has 1000 turns per metre and carries 2 A. The magnetic field inside it (μ₀ = 4π×10⁻⁷) is about:
Q79.
The cyclotron frequency of a charged particle in a magnetic field is:
Q80.
The magnetic field at the centre of a circular loop of radius 0.1 m carrying 5 A (μ₀ = 4π×10⁻⁷) is about:
Q81.
A rectangular coil of 100 turns and area 0.01 m² carries 1 A in a field of 0.5 T with its plane parallel to the field. The torque on it is:
Q82.
In a velocity selector, the electric field is 1000 V/m and the magnetic field is 0.5 T. Undeflected particles have speed:
Q83.
Two long parallel wires carry currents in the same direction. The wires:
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