Concept explainers
(a)
The rotational speed of the armature of the generator.
(a)
Answer to Problem 97P
The rotational speed of the armature of the generator is
Explanation of Solution
Write the expression for motional emf.
Here,
Substitute,
Conclusion:
Substitute,
Therefore, the rotational speed of the armature of the generator is
(b)
The average torque and instantaneous torque applied by bicycle tire to the generator.
(b)
Answer to Problem 97P
The average torque applied by bicycle tire to the generator is
Explanation of Solution
Write the expression for average torque.
Here,
Conclusion:
Substitute,
Substitute,
Therefore, the average torque applied by bicycle tire to the generator is
(c)
The linear speed of the bicycle to supply emf of
(c)
Answer to Problem 97P
The linear speed of the bicycle to supply emf of
Explanation of Solution
Write the expression for the linear speed of the bicycle.
Here,
Conclusion:
Substitute,
Therefore, the linear speed of the bicycle to supply emf of
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Chapter 20 Solutions
Physics
- How many turns must be wound on a flat, circular coil of radius 20 cm in order to produce a magnetic field of magnitude 4.0105 T at the center of the coil when the current through it is 0.85 A?arrow_forwardA stiff spring with a spring constant of 1200.0 N/m is connected to a bar on a slide generator as shown in Figure P32.40. Assume the bar has length l = 60.0 cm and mass m = 0.75 kg, and it slides without friction. The bar connects to a U-shaped wire to form a loop that has width w = 40.0 cm and total resistance 25 and that sits in a uniform magnetic field B = 0.35 T. The bar is initially pulled 5.0 cm to the left and released so that it begins to oscillate. What is the induced current in the loop as a function of time, I(t)? (Ignore any effects due to the magnetic force on the oscillating bar.)arrow_forwardSolenoid A has length L and N turns, solenoid B has length 2L and N turns, and solenoid C has length L/2 and 2N turns. If each solenoid carries the same current, rank the magnitudes of the magnetic fields in the centers of the solenoids from largest to smallest.arrow_forward
- In Figure P20.65 the rolling axle of length 1.50 m is pushed along horizontal rails at a constant speed v = 3.00 m/s. A resist or R = 0.400 is connected to the rails at points a and b, directly opposite each other. (The wheels make good electrical contact with the rails, so the axle, rails, and R form a closed-loop circuit. The only significant resistance in the circuit is R.) A uniform magnetic field B = 0.800 T is directed vertically downward. (a) Find the induced current I in the resistor. (b) What horizontal force F is required to keep the axle rolling at constant speed? (c) Which end of the resistor, a or b. is at the higher electric potential? (d) Alter the axle rolls past the resistor, does the current in R reverse direction? Explain your answer. Figure P20.65arrow_forwardA conducting rod of length = 35.0 cm is free to slide on two parallel conducting bars as shown in Figure P30.35. Two resistors R1 = 2.00 and R2 = 5.00 are connected across the ends of the bars to form a loop. A constant magnetic field B = 2.50 T is directed perpendicularly into the page. An external agent pulls the rod to the left with a constant speed of v = 8.00 m/s. Find (a) the currents in both resistors, (b) the total power delivered to the resistance of the circuit, and (c) the magnitude of the applied force that is needed to move the rod with this constant velocity. Figure P30.35arrow_forwardConsider the apparatus shown in Figure P30.32: a conducting bar is moved along two rails connected to an incandescent lightbulb. The whole system is immersed in a magnetic field of magnitude B = 0.400 T perpendicular and into the page. The distance between the horizontal rails is = 0.800 m. The resistance of the lightbulb is R = 48.0 , assumed to be constant. The bar and rails have negligible resistance. The bar is moved toward the right by a constant force of magnitude F = 0.600 N. We wish to find the maximum power delivered to the lightbulb. (a) Find an expression for the current in the lightbulb as a function of B, , R, and v, the speed of the bar. (b) When the maximum power is delivered to the lightbulb, what analysis model properly describes the moving bar? (c) Use the analysis model in part (b) to find a numerical value for the speed v of the bar when the maximum power is being delivered to the lightbulb. (d) Find the current in the lightbulb when maximum power is being delivered to it. (e) Using P = I2R, what is the maximum power delivered to the lightbulb? (f) What is the maximum mechanical input power delivered to the bar by the force F? (g) We have assumed the resistance of the lightbulb is constant. In reality, as the power delivered to the lightbulb increases, the filament temperature increases and the resistance increases. Does the speed found in part (c) change if the resistance increases and all other quantities are held constant? (h) If so, does the speed found in part (c) increase or decrease? If not, explain. (i) With the assumption that the resistance of the lightbulb increases as the current increases, does the power found in part (f) change? (j) If so, is the power found in part (f) larger or smaller? If not, explain. Figure P30.32arrow_forward
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