Question 1

A circuit contains two inductors of 6.0 mH inductance in parallel placed in series with an inductor of 8.0 mH inductance.After one of the 6.0 mH inductors burns out,the repairman wants to replace all three inductors with one inductor of equivalent inductance.Assuming inductors combine in series and parallel the same way resistors do,what inductance should he use?

Accepted Answer

Before the burn out, the two 6.0 mH inductors in parallel would have an equivalent inductance of:
1/L = 1/6.0 + 1/6.0
1/L = 0.3333
L = 3.0 mH
Now, adding the 8.0 mH inductor in series, the total equivalent inductance is:
L_total = 3.0 + 8.0 = 11 mH
Therefore, to replace all three inductors with one equivalent inductor, a 11 mH inductor should be used.

Question 2

The switch in the figure is closed at t = 0 when the current I is zero.When I = 15 mA,what is the potential difference across the inductor?

Accepted Answer

At t=0, the current through the inductor is zero, and due to its property, it will resist any change in current. So, when the switch is closed, the inductor initially resists the sudden increase in current, and the potential difference across it can be given by:
VL = L(dI/dt), where L is the inductance of the inductor.
Let's assume that the switch is closed for a sufficiently long time such that the current becomes constant. When the current becomes constant at 15 mA, the rate of change of current becomes zero, and hence, the potential difference across the inductor becomes zero (VL = L(dI/dt) = L*0 = 0). So, the potential difference across the inductor when the current is 15 mA is zero. Therefore, the correct answer is D.

Question 3

The magnetic field in a superconducting solenoid is 3.0 T.How much energy per unit volume is stored in the solenoid,in J/m³? $\mu$₀ = 4 $\pi$ *10 ^- ⁷ T . A/m

Accepted Answer

The answer of The magnetic field in a superconducting solenoid...

Question 4

When a switch is closed,completing an LR series circuit,the time needed for the current to reach one half its maximum value is ____ time constants.

Accepted Answer

The time constant for an LR series circuit is L/R. When the switch is closed, the current will ramp up exponentially, and it takes approximately 5 time constants for the current to reach its steady-state value. At one half the maximum value, the current has ramped up to approximately 0.63 times its steady-state value. Therefore, it takes approximately 0.693 time constants for the current to reach one half its maximum value in an LR series circuit.

Question 5

A circuit contains two inductors of 6.0 mH inductance in series placed in parallel with an inductor of 8.0 mH inductance.After one of the 6.0 mH inductors burns out,the repair person wants to replace all three inductors with one inductor of equivalent inductance.Assuming inductors combine in series and parallel the same way resistors do,what inductance should she use?

Accepted Answer

The answer of A circuit contains two inductors of 6.0...

Question 6

The figure shows an LR circuit with a switch and a 240-volt battery.At the instant the switch is closed the current in the circuit and the potential difference between points a and b,V_ab,are

Accepted Answer

The answer of The figure shows an LR circuit with...

Question 7

A car with a radio antenna 1.0 m long travels at 80 km/h in a locality where the Earth's magnetic field is 5.0 *10 ^- ⁵ T.What is the maximum possible emf induced in the antenna as a result of moving through the Earth's magnetic field?

Accepted Answer

The answer of A car with a radio antenna 1.0...

Question 8

When a switch is closed,completing an LR series circuit,the time needed for the current to reach three-quarters its maximum value is ____ time constants.

Accepted Answer

The answer of When a switch is closed,completing an LR...

Question 9

An inductor produces a back emf in a DC series RL circuit when a switch connecting the battery to the circuit is closed.We can explain this by

Accepted Answer

Lenz's law explains the generation of back emf as a reaction to changes in magnetic flux to oppose the change in current. The increasing magnetic flux within the coils of the inductor is a direct result of the increasing current in the coils, which together explain the phenomenon of back emf in an inductor in a DC series RL circuit.

Question 10

After a switch is thrown to remove the battery from a DC LR circuit,but the circuit is still left complete,the time constant represents

Accepted Answer

The time constant in an LR circuit represents the magnitude of the ratio of the current to the time rate of change of the current. It is a measure of how quickly the current will decay to zero after the battery is removed, not directly related to the time rate of change of the current or induced emf itself.

Question 11

A 500-turn circular loop 15.0 cm in diameter is initially aligned so that its axis is parallel to the Earth's magnetic field.In 2.77 ms the coil is flipped so that its axis is perpendicular to the Earth's field.If a voltage of 0.166 V is induced in the coil,what is the value of the Earth's magnetic field?

Accepted Answer

The answer of A 500-turn circular loop 15.0 cm in...

Question 12

When a switch is closed to complete a DC series RL circuit,

Accepted Answer

When a switch is closed in a DC series RL circuit, the electric field in the wires indeed increases to a maximum value as current starts to flow. Simultaneously, the magnetic field outside the wires also increases to a maximum value due to the current. The rate of change of both the electric and magnetic fields is greatest at the instant the switch is closed because that's when the circuit transitions from no current (and thus no fields) to a state where current begins to flow, initiating the build-up of these fields. Therefore, all of the statements are true.

Question 13

A bolt of lightning strikes the ground 200 m from a 100-turn coil oriented vertically and with the plane of the coil pointing toward the lightning strike.The radius of the coil is 0.800 m and the current in the lightning bolt falls from 6.02 *10⁶ A to zero in 10.5 $\mu$s.What is the voltage induced in the coil over this time period? [A question for future electrical engineers: is there any way to get lightning to strike repeatedly at the same point?]

Accepted Answer

The answer of A bolt of lightning strikes the ground...

Question 14

A rectangular coil of 100 turns measures 40.0 cm by 20.0 cm.This coil is placed next to an electromagnet which is switched on,increasing the magnetic field through the coil from zero to 0.800 T in 50.0 ms.If the resistance of the coil is 2.0 ohms,what are the induced voltage and current in the coil?

Accepted Answer

The answer of A rectangular coil of 100 turns measures...

Question 15

Find the magnetic energy stored in the air gap between two very large magnetic pole pieces,one North,one South,each with an area of 100 cm².Assume the 0.05 T magnetic field is uniform within the 2-cm gap.

Accepted Answer

The answer of Find the magnetic energy stored in the...

Question 16

A 10-mH inductor is connected in series with a 10-ohm resistor,a switch and a 6-volt battery.What is the time constant of the circuit? How long after the switch is closed will the current reach 99 percent of its final value?

Accepted Answer

The answer of A 10-mH inductor is connected in series...

Quiz 23: Faradays Law and Inductance

The switch in the figure is closed at t = 0 when the current I is zero.When I = 15 mA,what is the potential difference across the inductor?

The magnetic field in a superconducting solenoid is 3.0 T.How much energy per unit volume is stored in the solenoid,in J/m³? $\mu$ ₀ = 4 $\pi$ *10 ^- ⁷ T . A/m

When a switch is closed,completing an LR series circuit,the time needed for the current to reach one half its maximum value is ____ time constants.

The figure shows an LR circuit with a switch and a 240-volt battery.At the instant the switch is closed the current in the circuit and the potential difference between points a and b,V_ab,are

A car with a radio antenna 1.0 m long travels at 80 km/h in a locality where the Earth's magnetic field is 5.0 *10 ^- ⁵ T.What is the maximum possible emf induced in the antenna as a result of moving through the Earth's magnetic field?

When a switch is closed,completing an LR series circuit,the time needed for the current to reach three-quarters its maximum value is ____ time constants.

An inductor produces a back emf in a DC series RL circuit when a switch connecting the battery to the circuit is closed.We can explain this by

After a switch is thrown to remove the battery from a DC LR circuit,but the circuit is still left complete,the time constant represents

When a switch is closed to complete a DC series RL circuit,

A rectangular coil of 100 turns measures 40.0 cm by 20.0 cm.This coil is placed next to an electromagnet which is switched on,increasing the magnetic field through the coil from zero to 0.800 T in 50.0 ms.If the resistance of the coil is 2.0 ohms,what are the induced voltage and current in the coil?

Find the magnetic energy stored in the air gap between two very large magnetic pole pieces,one North,one South,each with an area of 100 cm².Assume the 0.05 T magnetic field is uniform within the 2-cm gap.

A 10-mH inductor is connected in series with a 10-ohm resistor,a switch and a 6-volt battery.What is the time constant of the circuit? How long after the switch is closed will the current reach 99 percent of its final value?

Quiz 23: Faradays Law and Inductance

The switch in the figure is closed at t = 0 when the current I is zero.When I = 15 mA,what is the potential difference across the inductor?

The magnetic field in a superconducting solenoid is 3.0 T.How much energy per unit volume is stored in the solenoid,in J/m3? μ\muμ 0 = 4 π\piπ *10 - 7 T . A/m

When a switch is closed,completing an LR series circuit,the time needed for the current to reach one half its maximum value is ____ time constants.

The figure shows an LR circuit with a switch and a 240-volt battery.At the instant the switch is closed the current in the circuit and the potential difference between points a and b,Vab,are

A car with a radio antenna 1.0 m long travels at 80 km/h in a locality where the Earth's magnetic field is 5.0 *10 - 5 T.What is the maximum possible emf induced in the antenna as a result of moving through the Earth's magnetic field?

When a switch is closed,completing an LR series circuit,the time needed for the current to reach three-quarters its maximum value is ____ time constants.

An inductor produces a back emf in a DC series RL circuit when a switch connecting the battery to the circuit is closed.We can explain this by

After a switch is thrown to remove the battery from a DC LR circuit,but the circuit is still left complete,the time constant represents

When a switch is closed to complete a DC series RL circuit,

Find the magnetic energy stored in the air gap between two very large magnetic pole pieces,one North,one South,each with an area of 100 cm2.Assume the 0.05 T magnetic field is uniform within the 2-cm gap.

A 10-mH inductor is connected in series with a 10-ohm resistor,a switch and a 6-volt battery.What is the time constant of the circuit? How long after the switch is closed will the current reach 99 percent of its final value?

The magnetic field in a superconducting solenoid is 3.0 T.How much energy per unit volume is stored in the solenoid,in J/m³? $\mu$ ₀ = 4 $\pi$ *10 ^- ⁷ T . A/m

The figure shows an LR circuit with a switch and a 240-volt battery.At the instant the switch is closed the current in the circuit and the potential difference between points a and b,V_ab,are

A car with a radio antenna 1.0 m long travels at 80 km/h in a locality where the Earth's magnetic field is 5.0 *10 ^- ⁵ T.What is the maximum possible emf induced in the antenna as a result of moving through the Earth's magnetic field?

Find the magnetic energy stored in the air gap between two very large magnetic pole pieces,one North,one South,each with an area of 100 cm².Assume the 0.05 T magnetic field is uniform within the 2-cm gap.