Mastering Physics Solutions: Understanding Changing Flux

Mastering Physics Solutions: Understanding Changing Flux

On March 6, 2013, in Chapter 20: Electromagnetic Induction and Waves, by Mastering Physics Solutions

Part A = There is no magnetic flux through the wire loop.
Part B = There is no induced current.
Part C = The induced current is counterclockwise.
Part D = B, B

When the switch is open, which of the following statements about the magnetic flux through the wire loop is true? Assume that the direction of the vector area of the wire loop is to the right.
What is the direction of the induced current in the wire loop (as seen from the left) when the switch is open?
Now the switch on the electromagnet is closed. What is the direction of the induced current in the wire loop immediately after the switch is closed (as seen from the left)?
Finally, the switch on the electromagnet is reopened. The magnitude of the external magnetic flux through the wire loop ______ (A. increases, B. decreases, C. remains constant), and there is _______ (A. zero, B. a clockwise, C. a counterclockwise) current induced in the loop (as seen from the left).

Click for More...

Tagged with:  

Mastering Physics Solutions: Rail Gun

Mastering Physics Solutions: Rail Gun

On March 1, 2013, in Chapter 20: Electromagnetic Induction and Waves, by Mastering Physics Solutions

Part A = out of the plane of the figure
Part B = The rod will accelerate but the magnitude of the acceleration will decrease with time; the velocity of the rod will approach but never exceed a certain terminal velocity.
Part C = (V – B * L * vr(t)) * (L * B) / (R * m)
Part D = V / (B * L)

There is a uniform magnetic field of magnitude B, pervading all space, perpendicular to the plane of rod and rails. The rod is released from rest, and it is observed that it accelerates to the left. In what direction does the magnetic field point?
Assuming that the rails have no resistance, what is the most accurate qualitative description of the motion of the rod?
What is the acceleration ar(t) of the rod? Take m to be the mass of the rod.
What is the terminal velocity vt reached by the rod?

Click for More...

 
Tagged with:  

Mastering Physics Solutions: Exercise 20.30

Mastering Physics Solutions: Exercise 20.30

On May 25, 2012, in Chapter 20: Electromagnetic Induction and Waves, by Mastering Physics Solutions

Part A = 20 V Click to use the calculator/solver for this part of the problem
Part B = 4200 turns Click to use the calculator/solver for this part of the problem
Part C = 1.6 A Click to use the calculator/solver for this part of the problem

The primary coil of an ideal transformer is connected to a 120-V source and draws 1.0 A. The secondary coil has 700 turns and supplies an output current of 6.0 A to run an electrical device.
What is the voltage across the secondary coil?
How many turns are in the primary coil?
If the maximum power allowed by the device (before it is destroyed) is 290 W, what is the maximum input current to this transformer?

Click for More...

Tagged with:  

Mastering Physics Solutions: Exercise 20.6

Mastering Physics Solutions: Exercise 20.6

On May 25, 2012, in Chapter 20: Electromagnetic Induction and Waves, by Mastering Physics Solutions

Part A = 0.33 m2 Click to use the calculator/solver for this part of the problem
Part B = 42 V Click to use the calculator/solver for this part of the problem
Part C = 83 V Click to use the calculator/solver for this part of the problem

A uniform magnetic field is at right angles to the plane of a wire loop. The field decreases by 0.25 T in 1.0*10^−3 s and the magnitude of the average emf induced in the loop is 83 V.

What is the area of the loop?
What would be the value of the average induced emf if the field change was the same but took twice as long to decrease?
What would be the value of the average induced emf if the field decrease was twice as much and it also took twice as long to change?

Click for More...

Tagged with:  

Mastering Physics Solutions: Exercise 20.7

Mastering Physics Solutions: Exercise 20.7

On May 23, 2012, in Chapter 20: Electromagnetic Induction and Waves, by Mastering Physics Solutions

Part A = 1.7 V Click to use the calculator/solver for this part of the problem
Part B = 0.44 V Click to use the calculator/solver for this part of the problem

A square loop of wire with sides of length 40 cm is in a uniform magnetic field perpendicular to its area.
If the field’s strength is initially 120 mT and it decays to zero in 0.011 s, what is the magnitude of the average emf induced in the loop?
What would be the average emf if the sides of the loop were only 20 cm?

Click for More...

Tagged with: