Free problems arranged by topic
 Kinematics Dynamics Conservation laws Thermodynamics Waves Electricity Magnetism Optics Fluids and elasticity Ideal gas AC current

 Free problems: all problems
 Kinematics Dynamics Conservation laws Thermodynamics Waves Electricity Magnetism Optics Fluids and elasticity Ideal gas AC current

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# Physics problems:magnetism

Magnetic Flux & Magnetic Induction

Problem 23.

What is the magnetic flux through the loop shown in the figure?

Solution

Problem 24.

Find the magnetic flux through the loop shown in the figure.

Solution

Problem 25.

What is the magnetic flux through the loop shown in the figure?

Solution

Problem 26.

There is a clockwise induced current in the conducting loop shown in the figure. Is the magnetic field inside the loop increasing or decreasing in strength?

Solution

Problem 27.

There is a counterclockwise induced current in the conducting loop shown in the figure. Is the magnetic field inside the loop increasing or decreasing in strength?

Solution

Problem 28.

There is a counterclockwise induced current in the conducting loop shown in the figure. Is the magnetic field inside the loop increasing or decreasing in strength?

Problem 29.

The magnitude of the magnetic field shown in the figure increases with time. What is the direction of current in the loop?

Solution

Problem 30.

The magnitude of the magnetic field shown in the figure increases with time. What is the direction of current in the loop?

Solution

Problem 31.

The magnetic field (see figure) is increasing at 0.3 T/s rate. What is the current in 5-cm-diameter loop? The loop’s resistance is 5 ohm.

Solution

Problem 32.

The current in 10-cm-diameter loop (see figure) is 0.02 A. The resistance of the loop is 10 Ohm. Find the rate of change of the magnetic field strength.

Solution

Problem 33.

The loop is bushed into a region of constant magnetic field of 0.5 T (see figure) with constant speed of 5 m/s. What is the magnitude of the current in the loop? The resistance of the loop is 10 ohm.

Solution

Problem 34.

What is the potential difference across a 5 mH inductor if the current through the inductor increases from 0.1 A to 0.8 A in 0.01 s?

Solution

Problem 35.

A 50 mH inductor is connected to 10 V battery. The resistance of the inductor is 5 ohm. What is the energy stored in the inductor?

Solution

Problem 36.

How much energy is stored in a solenoid that carries a current of 2 A? The solenoid has 1000 turns of wire, its diameter is 2 cm and its length is 10 cm.

Solution

Problem 37.

Find the time constant of the circuit shown in the figure.

Problem 38.

What is the time constant of the circuit shown in the figure?

Solution

Problem 39.

A 2-cm-diameter coil has 100 turns. A magnetic field, which is perpendicular to the coil, has the following time dependence: , where  is in tesla and time is in seconds. Find the induced current in the coil as a function of time. The resistance of the coil is 5 ohm.

Solution

Problem 40.

A 50-turn coil is at rest in a horizontal plane. A magnetic field  away from the vertical direction decreases from 1 T to 0.5 T in 0.2 seconds. What is the induced emf in the coil if the diameter of the coil is 10 cm?

Solution

Problem 41.

A 100-turn, the 10-cm-diameter coil has 20-ohm resistance. A magnetic field is perpendicular to the coil. At what rate must the magnetic field increase to induce 2 A current in the coil.

Solution

Problem 42.

A 4.0 cm x 4.0 cm square loop has a resistance of 5 ohm. One edge of the loop is parallel to a long straight wire and is at a distance of 10 cm from the wire. The current in the wire is increased at the rate of 50 A/s. What is the current in the loop?

Solution

Problem 43.

A rectangular loop is moving at a constant speed of 10 m/s (see figure) away from a long straight wire. A loop has a resistance of 20 ohm. What is the induced current in the loop at the moment of time shown in the figure?

Problem 44.

A small 1-mm-diameter circular loop is at the center of a large 20-cm-diameter loop. Both loops lie in the same plane. The current in outer loop changes from 2 A to 10 A in 5 seconds. What is the induced current in the inner loop if its resistance is 1 ohm?

Solution

Problem 45.

A square loop (see figure) moves into 0.5 T magnetic field at a constant speed of 5 m/s. Assuming that the loop enters the field at 0 s, find the induced current in the loop as a function of time. The resistance of the loop is 10 ohm.

Solution

Problem 46.

A magnetic field inside a 5-cm-diameter solenoid varies sinusoidally between 1 T and 3 T at a frequency of 20 Hz. Find the electric field strength as a function of time at a point 2 cm from the solenoid axis.

Solution

Problem 47.

A 4-cm-diameter solenoid has 2000 turns per meter. At a distance of 1 cm from the solenoid axis, the strength of an induced electric field is . What is the rate of change of the current through the solenoid?

Solution

Problem 49.

The current through 10 H inductor changes with time as , where the current is in A and the time is in seconds. Find the potential difference across the inductor.

Solution

Problem 61.

Two identical long wires of radius  are parallel and carry identical currents in opposite directions. Separation between the wires is . What is the inductance per unit length of the wires? Consider the flux only in the region between the wires.

Solution

Problem 62.

A conducting straight wire of length 20 cm is moving with a constant speed perpendicular to uniform 0.1 T magnetic field. The wire is perpendicular to the magnetic field. The voltage across the wire is 0.5 V. Find the speed of the wire.

Solution

Problem 63.

A conducting straight wire of length 20 cm is moving with a constant speed of 5 m/s perpendicular to uniform 0.2 T magnetic field. The wire is perpendicular to the magnetic field. Calculate the voltage across the wire.

Problem 64.

A flying airplane develops a 0.5 V potential difference between the tips of its wings. The vertical component of the magnetic field is  . Calculate the speed of the airplane if the distance between the tips of the wings is 12 m.

Problem 65.

An airplane flies horizontally with a speed of 900 km/h. The distance between the tips of the wings of the airplane is 12 m. The vertical component of the magnetic field is  . Calculate the potential difference between the tips of its wings.

Solution

Problem 66.

The current in a  inductor depends on time as . What is the voltage across the inductor at ?

Solution

Problem 67.

The current flowing through a  inductor depends on time as . How much energy is stored in the inductor at ? What is the voltage across the inductor at ?

Solution

Problem 72.

A 100-turn 10-cm-diameter solenoid is placed in a 0.01 T magnetic field, which is parallel to the axis of the solenoid. The solenoid rotates  in 5 seconds. Calculate the average emf generated across the solenoid.

Solution

Problem 73.

A 50 mH inductor is connected to a 20 V battery at zero moment of time. Find the current in the circuit at t=0.1 s. Neglect the resistance of the circuit and the internal resistance of the battery.

Solution

Problem 74.

A 100 mH inductor is connected to ideal 10 V battery at t=0. Find the moment of time when the current in the circuit is 0.5 A. Neglect the resistance of the circuit.

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