What is the principle reason why, when a small electric motor is first started up, the current through the armature is large for a moment and then settles to a much smaller value? a. the voltage applied to the armature is higher at first b. the temperature of the armature increases at first, thus increasing the resistance of the armature c. as the motor speeds up, it generates a higher EMF in the opposite direction to the applied voltage d. the counter EMF is higher at first

What is the principle reason why, when a small electric motor is first started up, the current through the armature is large for a moment and then settles to a much smaller value? a. the voltage applied to the armature is higher at first b. the temperature of the armature increases at first, thus increasing the resistance of the armature c. as the motor speeds up, it generates a higher EMF in the opposite direction to the applied voltage d. the counter EMF is higher at first

College Physics

1st Edition

ISBN:9781938168000

Author:Paul Peter Urone, Roger Hinrichs

Publisher:Paul Peter Urone, Roger Hinrichs

Chapter20: Electric Current, Resistance, And Ohm's Law

Section: Chapter Questions

Problem 66PE: Integrated Concepts (a) An aluminum power transmission line has a resistance of 0.0580/km. What is...

See similar textbooks

Similar questions

. The generator at a large power plant has an output of 1,000,000 kW at 24,000 V. (a) If it were a DC generator, what would he the current in it? (b) What is its energy output each day—in joules and in kilowatt—hours? (c) If this energy is sold at a price of 10 cents per kilowatt-hour, how much revenue does the power plant generate each day?
A large cyclotron directs a beam of He ++ nuclei onto a target with a beam current of 0.250 mA. (a) How many He++ nuclei per second is this? (b) How long does it take for 1.00 C to strike the target? (c) How long before 1.00 mol of He++ nuclei strike the target?
Integrated Concepts (a) An aluminum power transmission line has a resistance of 0.0580/km. What is its mass per kilometer? (b) What is the mass per kilometer of a copper line having the same resistance? A lower resistance would shorten the heating time. Discuss the practical limits to speeding the heating by lowering the resistance.
Unreasonable Results An inventor wants to generate 120V power by moving a 1.00mlong wire perpendicular to the Earth’s 5.00105T field. (a) Find the speed with which the wire must move. (b) What is unreasonable about this result? (c) Which assumption is responsible?
The energy in the capacitor is delivered by placing paddles on either side of the victim's heart as shown in the figure. The defibrillator delivers the charge stored in the capacitor through the paddles, hopefully resetting the heart so it can begin beating normally. The charge is delivered in a sudden pulse that lasts about 100 ms. What is the average current flowing through the body?‹I› = _____ A What is the rate at which the energy stored in the capacitor is transferred to the body? This is the average power output of the defibrillator.‹P› = _____ W What is the effective resistance of the body along the path that the current takes?Reff = _____ Ω
A motor operating on 240 V electricity has a 180 V back emf at operating speed and draws a 12.0 A current. (a) What is its resistance? (b) What current does it draw when it is first started?
A motor in normal operation carries a direct current of 0.750 A when connected to a 120 V power supply. The resistance in the motor windings is 17.2 . Determine the following values. (a) While in normal operation, what is the back emf generated by the motor? (b) While in normal operation, at what rate is internal energy produced in the windings? (c) What If? Suppose that a malfunction stops the motor shaft from rotating. At what rate will internal energy be produced in the windings in this case in kW (Most motors have a thermal switch that will turn off the motor to prevent overheating when this occurs.)
a student in the laboratory connects a 13 resistor, a 26 resistor, and a 36 resistor in parallel and then connects the arrangement to a 42 V dc source. what is the current (a)? what is the power (w)?
An AC appliance cord has its hot and neutral wires separated by 3.00 mm and carries a 5.00-A current. (a) What is the average force per meter between the wires in the cord?(b) What is the maximum force per meter between the wires? (c) Are the forces attractive or repulsive? (d) Do appliance cords need any special design features to compensate forthese forces?
ii, The electric current flowing in a resistor is given by I = 20 sin(100t) where I is in Amperes and t is in seconds. A, What is the maximum current? B, What is the frequency of the current? C, What is the time taken to change from zero to maximum current in each cycle?
A generator produces 250 kW of electric power at 7.2 kV. The current is transmitted to a remote village through wires with a total resistance of 15 Ω.a. What is the power loss due to resistance in the wires?b. What is the power loss if the voltage is increased to 30 kV?
An AC appliance cord has its live wire and neutral wire separated by 3.00 mm andcarries a 5.00 A current.a) What is the force per unit length between the wires?b) Are the forces between the two wires attractive or repulsive? Explain.c) Do appliance cords need any special design features to compensate for theseforces? Explain