Concept explainers
Videos
Simple electric motor
Obtain the equipment illustrated at right assemble it as shown.
You should have:
•a magnet, a battery, a switch, some connecting, and an ammeter.
• a copper wire coil. The ends of the wire leads to the coil have been stripped of the insulating enamel coating so that half the wire is bare.
• twoconducting supports for the leads to the coil
1. Examine the leads to the wire coil closely, so that you understand which portion of the wire has been stripped of the insulating coating.
For what orientations of the coil will there be a current through it due to the battery?
Check your answer by losing the switch and observing the deflection of the ammeter as you rotate the coil manually through one complete revolution.
2. Hold one pole of the magnet near the coil. Close the switch. If the coil does not begin to spin, adjust the location of the magnet or gently rotate the coil to Stan it spinning.
Use the ideas that we have developed in this and previous tutorials to explain the motion of the wire coil. (The questions that follow may serve as a guide to help you develop an understanding of the operation of the motor.)
When the coil is in the position shown, there is a current, I, through it.
a. The coil is manually started spinning so that it rotates clockwise.
During which portions of the cycle does the coil from a complete circuit with the battery such that there is a current through the wire of the coil?
The current results in a magnetic moment that interacts with the magnetic field of the magnet. Will the interaction tend to increase or to decrease the angular speed of the coil? Explain.
b. The coil is manually started spinning so that it rotates counterclockwise:
During which portions of the cycle does the coil form a complete circuit with the battery so that there is a current through the wire of the coil?
The current results in a magnetic moment that interacts with the magnetic field of the magnet. Will the interaction tend to increase or to decrease the angular speed of the coil? Explain.
Check that the behavior of your motor is consistent with your answers.
4. Consider the following questions about the motor:
• Why was insulated wire used for the coil? Would bare wire also work? Explain.
• Would you expect the motor to work if the leads to the coil were stripped completely? Explain.
5. Predict the effect on the motor of (i) reversing the leads to the battery and (ii) reversing the orientation of the magnet
Check your predictions.
Want to see the full answer?
Check out a sample textbook solution
Chapter 8 Solutions
Tutorials in Introductory Physics
Additional Science Textbook Solutions
Chemistry: Structure and Properties (2nd Edition)
Campbell Biology in Focus (2nd Edition)
Campbell Biology: Concepts & Connections (9th Edition)
Introductory Chemistry (6th Edition)
Organic Chemistry (8th Edition)
Human Physiology: An Integrated Approach (8th Edition)
- A bungee jumper plans to bungee jump from a bridge 64.0 m above the ground. He plans to use a uniform elastic cord, tied to a harness around his body, to stop his fall at a point 6.00 m above the water. Model his body as a particle and the cord as having negligible mass and obeying Hooke's law. In a preliminary test he finds that when hanging at rest from a 5.00 m length of the cord, his body weight stretches it by 1.55 m. He will drop from rest at the point where the top end of a longer section of the cord is attached to the bridge. (a) What length of cord should he use? Use subscripts 1 and 2 respectively to represent the 5.00 m test length and the actual jump length. Use Hooke's law F = KAL and the fact that the change in length AL for a given force is proportional the length L (AL = CL), to determine the force constant for the test case and for the jump case. Use conservation of mechanical energy to determine the length of the rope. m (b) What maximum acceleration will he…arrow_forward210. Sometimes the Helmholtz free energy F(T, V, N) divided by temperature, T, is an interesting quantity. For example, the quantity is proportional to the logarithm of the equilibrium constant or solubilities. A. Derive a relationship showing that Find the constant of proportionality. a F αυ ƏT T B. Suppose F(T) depends on temperature in the following way: F(T)=2aT²+bT. Find S(T) and U(T).arrow_forwardchoosing East (e) is not correct!arrow_forward
- disks have planes that are parallel and centered Three polarizing On a common axis. The direction of the transmission axis Colish dashed line) in each case is shown relative to the common vertical direction. A polarized beam of light (with its axis of polarization parallel to the horizontal reference direction) is incident from the left on the first disk with int intensity So = 790 W/m². Calculate the transmitted intensity if 81=28.0° O2-35.0°, and O3 = 40.0° w/m² horizontal Өз 02arrow_forwardA polarized light is incident on several polarizing disks whose planes are parallel and centered on common axis. Suppose that the transmission axis of the first polarizer is rotated 20° relative to the axis of polarization of the incident and that the transmission axis of each exis of light, additional analyzer is rotated 20° relative to the transmission axis the previous one. What is the minimum number of polarizer needed (whole number), so the transmitted light through all polarizing sheets has an Striking intensity that is less then 10% that the first polarizer?arrow_forwardA high energy pulsed laser emits 1.5 nano second-long pulse of average power 1.80x10" W. The beam is cylindrical with 2.00 mm in radius. Determine the rms value of the B-field? -Tarrow_forward
- A 23.0-mw (mill:-Watts) laser puts out a narrow cyclindrical beam 50 mm in diameter. What is the average N/C. rms E-field?arrow_forwardThe average intensity of light emerging from a polarizing sheet is. 0.550 W/m², and the average intensity of the horizontally polarized light incident on the sheet is 0.940 W/m². Determine the angle that the transmission axis of the polarizing sheet makes with the horizontalarrow_forwardwe measure an At a particular moment in time and space, electromagnetic wave's electric and magnetic fields. We find the electric field & pointing North and the magnetic field B pointing Down. What is the direction of wave propagation? a. South b. West C. c. Up d. Down e. East f. North.arrow_forward
- Hello, please help with how to calculate impact velocity and rebound velocity. Thanks!arrow_forwardA object of mass 3.00 kg is subject to a force FX that varies with position as in the figure below. Fx (N) 4 3 2 1 x(m) 2 4 6 8 10 12 14 16 18 20 i (a) Find the work done by the force on the object as it moves from x = 0 to x = 5.00 m. J (b) Find the work done by the force on the object as it moves from x = 5.00 m to x = 11.0 m. ] (c) Find the work done by the force on the object as it moves from x = 11.0 m to x = 18.0 m. J (d) If the object has a speed of 0.400 m/s at x = 0, find its speed at x = 5.00 m and its speed at x speed at x = 5.00 m speed at x = 18.0 m m/s m/s = 18.0 m.arrow_forwardAn EL NIÑO usually results in Question 8Select one: a. less rainfall for Australia. b. warmer water in the western Pacific. c. all of the above. d. none of the above. e. more rainfall for South America.arrow_forward
Physics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage Learning
Principles of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning
Physics for Scientists and Engineers, Technology ...PhysicsISBN:9781305116399Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning
Glencoe Physics: Principles and Problems, Student...PhysicsISBN:9780078807213Author:Paul W. ZitzewitzPublisher:Glencoe/McGraw-Hill
College PhysicsPhysicsISBN:9781285737027Author:Raymond A. Serway, Chris VuillePublisher:Cengage Learning