Problem 24.48 A device called a railgun uses the magnetic force on currents to l

Question

Problem 24.48

A device called a railgun uses the magnetic force on currents to launch projectiles at very high speeds. An idealized model of a railgun is illustrated in (Figure 1) . A 1.2 V power supply is connected to two conducting rails. A segment of copper wire, in a region of uniform magnetic field, slides freely on the rails. The wire has a 0.78 m resistance and a mass of 4.8 g . Ignore the resistance of the rails. The power supply is switched on.

Part A

What is the current?

Express your answer with the appropriate units.

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Part B

What is direction of the force on the wire?

What is direction of the force on the wire?

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Part C

What is the magnitude of the force on the wire?

Express your answer with the appropriate units.

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Part D

What will be the wire's speed after it has slid a distance of 7.0 cm ?

Express your answer with the appropriate units.

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Figure 1 of 1

Problem 25.2 - Enhanced - with Feedback

Part A

What is the magnitude of the emf induced between the two sides of the shark's head?

Express your answer using two significant figures.

Problem 25.20 - Enhanced - with Feedback

Part A

Is the magnetic field strength increasing or decreasing?

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Part B

What is the rate of change of the field, B/t?

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Figure 1 of 1

Problem 25.24 - Enhanced - with Feedback

Part A

What emf is induced in a square 180 km on a side by this rate of change of field?

Express your answer with the appropriate units.

Problem 25.72

A light-emitting diode (LED) connected to a 3.0 Vpower supply emits 440 nm blue light. The current in the LED is 21 mA , and the LED is 51 %efficient at converting electric power input into light power output.

Part A

How many photons per second does the LED emit?

Problem 24.48

A device called a railgun uses the magnetic force on currents to launch projectiles at very high speeds. An idealized model of a railgun is illustrated in (Figure 1) . A 1.2 V power supply is connected to two conducting rails. A segment of copper wire, in a region of uniform magnetic field, slides freely on the rails. The wire has a 0.78 m resistance and a mass of 4.8 g . Ignore the resistance of the rails. The power supply is switched on.

Part A

What is the current?

Express your answer with the appropriate units.

I =

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Part B

What is direction of the force on the wire?

What is direction of the force on the wire?

left up right down

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Part C

What is the magnitude of the force on the wire?

Express your answer with the appropriate units.

F =

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Part D

What will be the wire's speed after it has slid a distance of 7.0 cm ?

Express your answer with the appropriate units.

vf =

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Figure 1 of 1

Problem 25.2 - Enhanced - with Feedback

A scalloped hammerhead shark swims at a steady speed of 1.8 m/s with its 89-cm-wide head perpendicular to the earth's 56 T magnetic field.

You may want to review (pages 806 - 809) .

Part A

What is the magnitude of the emf induced between the two sides of the shark's head?

Express your answer using two significant figures.

E =   mV  

Problem 25.20 - Enhanced - with Feedback

The loop in the figure has an induced current as shown. The loop has a resistance of 0.14 .(Figure 1)

You may want to review ( pages 815 - 817) .

Part A

Is the magnetic field strength increasing or decreasing?

Is the magnetic field strength increasing or decreasing? increasing decreasing

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Part B

What is the rate of change of the field, B/t?

|B/t| =   T/s  

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Figure 1 of 1

15cm/ × 1.2V B = 0.80 T

Explanation / Answer

24.48 :

(A) I = V / R

I = 1.2 / (0.78 x 10^-3 )

I = 1538.5 A

(B) IL -> downward

B -> into the page

F = IL X B = to the right

(C) F = (1538.5 x 0.15)(0.80) = 184.6 N

(d) a = F/m = 184.6 / (4.8 x 10^-3 ) = 38461.5 m/s^2

v^2 - vi^2 = 2 a d

v^2 - 0 = 2 (38461.5) (0.07)

v = 73.4 m/s

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