Exam 29: Changing Magnetic Fields

An insulated wire of diameter 1.0 mm and negligible resistance is wrapped tightly around a cylindrical core of radius 5.0 cm and length 30 cm to build a solenoid. What is the energy stored in this solenoid when a current I = 0.20 A flows through it? (μ₀ = 4π × 10^-7 T • m/A)

A 50-cm wire placed in an east-west direction is moved horizontally to the north with a speed of 2)0 m/s. The horizontal component of the earth's magnetic field at that location is 25 μT toward the north and the vertical component is 50μT downward.What is the emf induced between the ends of the wire?

The long straight wire in the figure carries a current I that is decreasing with time at a constant rate.The circular loops A,B,and C all lie in a plane containing the wire.The induced emf in each of the loops A,B,and C is such that

A circular loop of radius 0.10 m is rotating in a uniform external magnetic field of 0.20 T. Find the magnetic flux through the loop due to the external field when the plane of the loop and the magnetic field vector are (a)parallel. (b)perpendicular. (c)at an angle of 30° with each other.

What is the self-inductance of a solenoid 30.0 cm long having 100 turns of wire and a cross-sectional area of 1.00 × 10^-4 m²? (μ₀ = 4π × 10^-7 T • m/A)

A bar magnet is held vertically with its upper end a little bit below the center of a horizontal metal ring.The upper end of the magnet is its north pole,as shown in the figure.The bar magnet is now dropped.An observer views the ring from above its center.To this observer,how will the induced current in the ring behave as the magnet falls?

The coil in a 60-Hz ac generator has 125 turns,each having an area of 3.0 × 10^-2 m² and is rotated in a uniform 0.12-T magnetic field.What is the peak output voltage of this generator?

A large magnetic flux change through a coil must induce a greater emf in the coil than a small flux change.

In the figure,two parallel wires carry currents of magnitude I in opposite directions.A rectangular loop is midway between the wires.The current I is decreasing with time.The induced current through the resistor R is

Wire is wound on a square frame,30 cm by 30 cm,to form a coil of 7 turns.The frame is mounted on a horizontal shaft through its center (perpendicular to the plane of the diagram),as shown in the figure.The coil is in clockwise rotation,with a period of 0.060 s.A uniform,horizontal,magnetic field of magnitude 0.40 T is present.At a given instant,the plane of the coil forms a 60° angle with the horizontal,as shown.At that instant,what is the magnitude of the emf induced in the coil?

In the figure,the inner loop carries a clockwise current I that is increasing.The resistor R is in the outer loop and both loops are in the same plane.The induced current through the resistor R is

A solenoid of length 0.700 m having a circular cross-section of radius 5.00 cm stores 6.00 µJ of energy when a 0.400-A current runs through it.What is the winding density of the solenoid? (μ₀ = 4π × 10^-7 T • m/A)

What is the energy density in the magnetic field 25 cm from a long straight wire carrying a current of 12 A? (μ₀ = 4π × 10^-7 T • m/A)

At a certain instant the current flowing through a 5.0-H inductor is 3.0 A.If the energy in the inductor at this instant is increasing at a rate of 3.0 J/s,how fast is the current changing?

For a long ideal solenoid having a circular cross-section,the magnetic field strength within the solenoid is given by the equation B(t)= 5.0t T,where t is time in seconds.If the induced electric field outside the solenoid is 1.1 V/m at a distance of 2.0 m from the axis of the solenoid,find the radius of the solenoid.

A closed loop conductor that forms a circle with a radius of 2.0 m is located in a uniform but changing magnetic field.If the maximum emf induced in the loop is 5.0 V,what is the maximum rate at which the magnetic field strength is changing if the magnetic field is oriented perpendicular to the plane in which the loop lies?

In the figure,a copper bar is in contact with a pair of parallel metal rails and is in motion with Velocity ν.A uniform magnetic field is present pointing downward,as shown.The bar,the rails, And the resistor R are all in the same plane.The induced current through the resistor R is

A ten-loop coil having an area of 0.23 m² and a very large resistance is in a 0.047-T uniform magnetic field oriented so that the maximum flux goes through the coil.The coil is then rotated so that the flux through it goes to zero in 0.34 s.What is the magnitude of the average emf induced in the coil during the 0.34 s?