Exam 30: Electromagnetic Induction

In the figure,the current in a solenoid having no appreciable resistance is flowing from b to a and is decreasing at a rate of 9.6 A/s.The self-induced emf in the solenoid is found to be 8.4 V. (a)What is the self-inductance of the solenoid? (b)Which point,a or b is at higher potential?

In the figure,a straight wire carries a current I.The wire passes through the center of a toroidal coil.If the current in the wire is quickly reduced to zero,the induced current through the resistor R is

For the circuit shown in the figure,the switch has been open for a very long time. (a)What is the potential drop across the 15.0-mH inductor just after closing the switch? (b)What is the potential drop across the 70.0-µF capacitor after the switch has been closed for a very long time?

For the circuit shown in the figure,the inductors have no appreciable resistance and the switch has been open for a very long time. (a)The instant after closing the switch,what is the current through the 60.0-Ω resistor? (b)The instant after closing the switch,what is the potential difference across the 15.0-mH inductor? (c)After the switch has been closed and left closed for a very long time,what is the potential drop across the 60.0-Ω resistor?

A conducting bar moves along frictionless conducting rails connected to a 4.00-Ω resistor as shown in the figure.The length of the bar is 1.60 m and a uniform magnetic field of 2.20 T is applied perpendicular to the paper pointing outward,as shown. (a)What is the applied force required to move the bar to the right with a constant speed of 6.00 m/s? (b)At what rate is energy dissipated in the 4.00 Ω resistor?

An ideal solenoid is 18.5 cm long,has a circular cross-section 2.20 cm in diameter,and contains 545 equally spaced thin windings.This solenoid is connected in a series circuit with an open switch,a 15.0-Ω resistor,and a battery of internal resistance 5.00 Ω and open-circuit terminal voltage of 25.0 V.(μ₀ = 4π × 10^-7 T ∙ m/A) (a)What is the maximum amount of energy that the solenoid will store after closing the switch? (b)How long after closing the switch will it take for the stored energy in the solenoid to reach one-half of its maximum value?

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)

An LR circuit contains an ideal 60-V battery,a 42-H inductor having no resistance,a 24-Ω resistor,and a switch S,all in series.Initially,the switch is open and has been open for a very long time.At time t = 0 s,the switch is suddenly closed.How long after closing the switch will the potential difference across the inductor be 24 V?

In the figure,a bar magnet moves away from the solenoid.The induced current through the resistor R is

A circular loop of wire lies in the plane of the paper.An increasing magnetic field points out of the paper.What is the direction of the induced current in the loop?

A uniform magnetic field is applied perpendicular to the plane of a 60-turn circular coil with a radius of 6.0 cm and a resistance of 0.60 Ω.If the magnetic field increases uniformly from 0.20 T to 1.8 T in 0.20 s,what is the magnitude of the emf induced in the coil?

A 200-loop coil of cross sectional area 8.5 cm² lies in the plane of the page.An external magnetic field of 0.060 T is directed out of the plane of the page.The external field decreases to 0.020 T in 12 milliseconds. (a)What is the magnitude of the change in the external magnetic flux enclosed by the coil? (b)What is the magnitude of the average voltage induced in the coil as the external flux is changing? (c)If the coil has a resistance of 4.0 ohms,what is the magnitude of the average current in the coil?

An LR circuit contains an ideal 60-V battery,a 51-H inductor having no resistance,a 21-Ω resistor,and a switch S,all in series.Initially,the switch is open and has been open for a very long time.At time t = 0 s,the switch is suddenly closed.When the voltage across the resistor is equal to the voltage across the inductor,what is the current in the circuit?

A capacitor is charging in a simple RC circuit with a dc battery.Which one of the following statements about this capacitor is accurate?

A coil of 160 turns and area 0.20 m² is placed with its axis parallel to a magnetic field of initial magnitude 0.40 T.The magnetic field changes uniformly from 0.40 T in the +x direction to 0.40 T in the -x direction in 2.0 s.If the resistance of the coil is 16 Ω,at what rate is power generated in the coil?

A loop of radius r = 3.0 cm is placed parallel to the xy-plane in a uniform magnetic field = 0.75 T .The resistance of the loop is 18 Ω.Starting at t = 0,the magnitude of the field decreases uniformly to zero in 0.15 seconds.What is the magnitude of the electric current produced in the loop during that time?

A transformer changes the 10,000 V power line to 120 V.If the primary coil contains 750 turns,how many turns are on the secondary?

In the figure,two solenoids are side by side.The switch S,initially open,is closed.The induced current through the resistor R is

A circular metal ring is situated above a long straight wire,as shown in the figure.The straight wire has a current flowing to the right,and the current is increasing in time at a constant rate.Which statement is true?

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)