Concept explainers
(a)
The effect on the induced emf of a generator if the flux per pole is doubled.
(a)
Answer to Problem 12SP
Solution:
Doubled
Explanation of Solution
Given data:
The flux per pole is doubled.
Formula used:
The induced emf of the generator is expressed as
Here,
Explanation:
Consider the expression for induced emf of the generator at its initial condition:
Consider the expression for induced emf of the generator when flux per pole is doubled:
From equation (1) and (2),
Understand that the magnetic flux per pole is doubled. Hence, magnetic field should be doubled.
Substitute
Solve for
Conclusion:
Therefore, if the flux per pole is doubled, the induced emf of a generator doubles as well.
(b)
The effect on the induced emf of a generator if the speed of the armature is doubled.
(b)
Answer to Problem 12SP
Solution:
Doubled
Explanation of Solution
Given data:
The speed of the armature is doubled.
Formula used:
The induced emf of the generator is expressed as
Here,
Explanation:
Consider the expression for induced emf of the generator at its initial condition:
Consider the expression for induced emf of the generator when the speed of the armature is doubled, assuming the doubling of speed will not have much effect on the cosine term of the induced emf for small speed. Therefore,
From equation (3) and (4),
Substitute
Solve for
Conclusion:
Therefore, if the speed of the armature is doubled, the induced emf of a generator will also be double.
Want to see more full solutions like this?
Chapter 33 Solutions
Schaum's Outline of College Physics, Twelfth Edition (Schaum's Outlines)
- Unreasonable Results A surveyor 100 m from a long straight 200-kV DC power line suspects that its magnetic field may equal that of the Earth and affect compass readings. (a) Calculate the current in the wire needed to create a 5.00105T field at this distance. (b) What is unreasonable about this result? (c) Which assumption or premise is responsible?arrow_forwardYou intend to move a rectangular loop of wire into a region of uniform magnetic field at a given speed so as to induce an emf in the loop. The plane of the loop must remain perpendicular to the magnetic field lines. In which orientation should you hold the loop while you move it into the region with the magnetic field to generate the largest emf? (a) with the long dimension of the loop parallel to the velocity vector (b) with the short dimension of the loop parallel to the velocity vector (c) either way because the emf is the same regardless of orientationarrow_forwardConstruct Your Own Problem Consider a double transformer to be used to create very large voltages. The device consists of two stages. The first is a transformer that produces a much larger output voltage than its input. The Output of the first transformer is used as input to a second transformer that further increases the voltage. Construct a problem in which you calculate the output voltage of the final stage based on the input voltage of the first Stage and the number of turns or loops in bath parts of both transformers (four coils in all). Also calculate the maximum output current of the final stage based on the input current. Discuss the possibility of power losses in the devices and the effect on the output current and power.arrow_forward
- A 120-V, series-wound dc motor draws 0.50 A from its power source when operating at full speed, and it draws 2.0 A when it starts. The resistance of the armature coils is 10 , (a) What is the resistance of the field coils? (b) What is tire back emf of the motor when it is running at full speed? (c) The motor operates at a different speed and draws 1.0 A from the source. What is the back emf in this case?arrow_forwardConstruct Your Own Problem Consider using the torque on a current-carrying coil in a magnetic field to detect relatively small magnetic fields (less than the field of the Earth, for example). Construct a problem in which you calculate the maximum torque on a current- carrying loop in a magnetic field. Among the things to be considered are the size of the coil, the number of loops it has, the current you pass through the coil, and the size of the field you wish to detect. Discuss whether the torque produced is large enough to be effectively measured. Your instructor may also wish for you to consider the effects, if any, of the field produced by the coil on the surroundings that could affect detection of the small field.arrow_forwardMeasurements affect the system being measured, such as the current loop in Figure 22.56. (a) Estimate file field the loop creates by calculating the field at the center of a circular loop 20.0 cm in diameter carrying 5.00 A. (b) What is the smallest field strength this loop can be used to measure, if its field must alter the measured field by less than 0.0100%?arrow_forward
- The current I through a long solenoid with n trims per meter and radius R is changing with time as given by dI/dt. Calculate the induced electric field as a function of distance r from the central axis of the solenoid.arrow_forward(a) A dc power line for a light-rail system caries 1000 A at an angle of 30.0 to Earth's 5.0105 T field, What is the force on a 100-m section of this line? (b) Discuss practical concerns this presents, if any.arrow_forwardIntegrated Concepts This problem refers to the bicycle generator considered in the previous problem. It is driven by a 1.60 cm diameter wheel that rolls on the outside rim of the bicycle tire. (a) What is the velocity 0f the bicycle if the generator’s angular velocity is 1875 rad/s? (b) What is the maximum emf of the generator when the bicycle moves at 10.0 m/s, noting that it was 18.0 V under the original conditions? (c) If the sophisticated generator can vary its own magnetic field, what field strength will it need at 5.00 m/s to produce a 9.00 V maximum emf?arrow_forward
- (a) A DC power line for a light-rail system carries 1000 A at an angle of 30.0° to the Earth’s 5.00105-T field. What is the force on a 100-m section of this line? (b) Discuss practical concerns this presents, if any.arrow_forwardAn example of magnetohydrodynamics (MHD) comes from the flow of a river (salty water). This fluid interacts with the Earth’s magnetic field to produce a potential difference between the two river banks. How would you go about calculating the potential difference?arrow_forwardAn N-turn circular wire coil of radius r lies in the xy-plane (the plane of the page), as in Figure P20.10. A uniform magnetic field is turned on, increasing steadily from 0 to B0 in the positive z-direction in t seconds. (a) Find a symbolic expression for the emf, , induced in the coil in terms of the variables given. (b) looking down on at the xy-plane from the positive z-axis, is the direction of the induced current clockwise or counterclockwise? (c) If each loop has resistance R, find an expression for the magnitude of the induced current, I.arrow_forward
- College PhysicsPhysicsISBN:9781938168000Author:Paul Peter Urone, Roger HinrichsPublisher:OpenStax CollegeCollege PhysicsPhysicsISBN:9781285737027Author:Raymond A. Serway, Chris VuillePublisher:Cengage LearningPrinciples of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning
- College PhysicsPhysicsISBN:9781305952300Author:Raymond A. Serway, Chris VuillePublisher:Cengage LearningPhysics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage Learning