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# EMF

### Electromagnetic Induction: Induced EMF in a rotating loop

1. A rectangular loop with surface area A lies in the x,y-plane with two sides parallel to the x-axis and the other two parallel to the y-axis in the presence of a uniform magnetic field with a magnitude B directed along the positive x-axis. The loop is made to rotate around an axis that is parallel to the y-axis and bisects the

### 2 Problems

1. What is the definition of displacement current and how does it arise? Does displacement current have any real significance? Explain 2. Write down the maxwell's equations of electromagnetism, and state the laws they represent. Explain the meaning of all the symbols used.

### RCL series circuit

When an RCL series circuit is connected to a 120 V rms 60 Hz line, the rms current is 11.0 A and the current leads the emf by 45 degrees. a) Find the power supplied to the circuit. b) What is the resistance? c) If the inductance is 0..05H, find the capacitance. d) What capacitance would you add, and how, to make the po

### Electromagnetic Induction: Flux, EMF and Mutual Inductance

Please help me with the attached problem. There are two pages to the problem, having parts A-E.

### Calculating the current of a circuit

A 50.0 H inductor and a 12.5 ohm resistor are connected in a series. A power source of constant 22.5 volts is applied across the series RL circuit elements at time t=0. What is the current in the circuit 10.0 seconds after the power is applied?

### Lenz's Law for Magnetic Flux

The magnetic flux through the loop increases according to the relation (see attachment for remainder of the question). a) What is the magnitude of the emf induced in the loop when t= 2.05? b) Is the direction of the current through R to the right or left?

### Induction and Energy Transfer

A metal rod is forced to move constant velocity V along two parallel metal rails, connected with a strip of metal at one end. A magnetic field of magnitude B = .350T points out of the page. a) if the rails are separated by a 25.0 cm and the speed of the rod is 55.0 cm/s, what emf is generated? b) if the rod has a resista

### Electromagnetic Induction: Induced EMF and Current

Two parallel loops of wire having the same common axis. The smaller loop of (raduis r ) and is above the larger loop (raduis R) by a distance X>>R. The magnetic field due to the counterclockwise current i in the larger loop is nearly uniform throughout the smaller loop. Suppose that x is increasing at a constant rate dx/dt = v.

### DC Circuits: Time Varying Current and Voltages

Consider the circuit of Figure P4.18 in which the switch has been open for a long time prior to t=-0. Determine the values of vc(t) before t=0 and a long time after t=0. Also, determine the time constant after the switch closes and expressions for vc(t). Sketch vc(t) to scale versus time for -2 <= t <= 5. Consider the circuit

### 16 good questions on electromagnetism

(See attached file for full problem description with proper symbols and diagrams) --- 3.1 A long wire carries a current of 2 A along the +z axis. Calculate B in free space at (3,4,9). 3.2 Inside a long conductor of radius a, the magnetic field is H = 5 rho;/(2pi a2) a(phi) A/m. (a) Determine the current density J. (b) D

### loop of 500 turns is placed in a magnetic field

See attached file for proper format of formulas. A loop of 500 turns is placed in a magnetic field that follows the equation: (See attachment) The radius of the loop is 0.75 m. a) What is the relation of the induced emf in that loop? b) What is the induced emf of the loop at 2 sec? c) If the wire has a resistance o

### EMF Thevenin's Diagram

(See attached file for full problem description) --- Refer to diagram below: 1. Use thevenin's theorem to calculate the thevenin emf and impedance for the circuit contained in the box to the left of the terminals A&B. Assume that L is a pure inductor. 2. Sketch the complete thevenin circuit plus load and calculate:

### Changing magnetic field

Transcranial magnetic stimulation (TMS) is a noninvasive method for studying brain function, and possibly for treatment as well. In this technique, a conducting loop is held near a person's head. When the current in the loop is changed rapidly, the magnetic field it creates can change at a rate of {see attachment}. This rapidly

### Faraday's Law of Electromagnetic Induction 2

A constant magnetic field passes through a single rectangular loop whose dimensions are 0.35 m x 0.55 m. The magnetic field has a magnitude of 2.1 T and is inclined at an angle of 70° with respect to the normal to the plane of the loop. (a) If the magnetic field decreases to zero in a time of 0.52 s, what is the magnitud

### Phasor Diagram for Synchronous Generator

A 60-Hz 24-kV 250-MVA Y-Connected salient-pole synchronous generator (Xd=1.75 per unit, Xq=1.40 per unit) is operating with a phase-A to a neutral voltage of 14 cos wt kV and a phase-A current of 5.75 cos wt kA; the currents and voltages are balanced at three-phase. The rotor angle is known to be wt+37 degrees. a) Draw a pha

### Light and Electricity

1. A proton of charge + 1.6 x 10^(-19) C and mass 1.67 x 10(-27)kg is introduced into a region of B = 1.5 T with an initial velocity of 1.25 x 10^6 m/s perpendicular to B. What is the radius of the proton's path? 2. A coil 17 cm in diameter and wound with 12 turns of wire is placed with the plane of the coil at right angles t

### Electrical Energy Conversion - Shunt Motor

Please refer to the attached file. A 50 hp, 240 V, 650 rpm DC shunt motor operating at rated load draws a line current... (see attached)

### Description of Electromagnetics

The EMF of a 377 ohm generator is a single pulse of 1 microsecond duration. The generator drives an infinite, 3 * 10e8 m/s, 377 ohm transmission line. Connected across the line, 1km away from the generator is a 754 ohm resistor. Another 754 ohm resistor is connected across the line 150m further away. The energy of the pulse laun

### Description of Resistors

Hi. Can someone please walk me through how to do the following problem? Two resistors are connected in series to a battery with an emf of 12 V. The voltage across the first resistor is 2.2 V and the current through the second resistor is 0.15 A. Find the resistance of the two resistors. Thank you.

### Determine the voltage drop (from top to bottom) across the resistor.

Determine the voltage drop (from top to bottom) across the 16ohm resistor. Also, determine the voltage drop (from top to bottom) across the 4ohm resistor. Referring to the circuit, what is the voltage v? Show how you arrived at your answer.

### Induction

A 25-turn circular coil of wire has diameter 1.00 m. It is placed with its axis along the direction of the Earth's magnetic field of 50.0 &#956;T, and then in 0.200 s it is flipped 180°. An average emf of what magnitude is generated in the coil?

### Magnetism

A 17.2 cm diameter circular loop of wire is in a 1.13 T magnetic field. It is removed from the field in 0.110s. What is the average induced emf?

### Calculating the induced emf - Magnetism

The magnetic field perpendicular to a circular loop of wire 17.6cm in diameter is changed from +0.510 T to -0.450 T in 117rms, where + means the field points away from an observer and - toward the observer. Calculate the induced emf.

### Magnetic field : key information

A 6.30cm diameter wire coil is initially oriented so that its plane is perpendicular to a magnetic field of 0.740T pointing up. During the course of 0.130s, the field is changed to one of 0.310 T pointing down. What is the average induced emf in the coil?

### EMF in a current-carrying system.

A bar is moving across a open-ended loop with resistance R in a presence of a constant perpendicular magnetic field. a. At what speed should the bar be moved to produce a current of 0.500 A? b. What is the motional emf? c. What is the power dissipated by the resistor? d. What force must be applied to the bar?

### Magnetism: Current flowing through a resistor, surface charge distribution, constant speed of the bar

A metal bar of mass m and length L slides without friction but with good electrical contact between two vertical metal posts. The bar and posts have negligible resistance. The posts are connected at the bottom by a resistor R. Assume the bar falls at constant speed v, and that there is a magnetic field coming out of the page.

### bar sliding in a magnetic field on rails - Voltage induced

Imagine that we have two metal rails 20 cm apart connected by a light bulb. The rails are placed in a 1.0 T magnetic field oriented vertically downward. We then constrain a bar to slide on the rails toward the lightbulb in this magnetic field. How fast do we have to move the bar to put a voltage difference of 3.0 V across the

### current in a 48.1 mH inductor changes with time

The current in a 48.1 mH inductor changes with time as I = bt^2 - at. With a = 2.7 A/s and b = 3 A/s^2, find the magnitude of the induced emf at t = .992 s. Units of V At what time is the emf zero? Units of s

### Determining Rate of Magnitude Change in Rectangular Coil

The plane of a rectangular coil of dimension 5 cm by 8 cm is perpendicular to the direction of a magnetic field B. The coil has 29.7 turns and a total resistance of 12.8 Ohms. At what rate must the magnitude of B change in order to induce a current of .227 A in the windings of the coil in units of T/s?

### Induced emf

A two turn circular wire loop of radius .262 m lies in a plane perpendicular to a uniform magnetic field of magnitude .373 T. Now the wire is reshaped from a two turn circle to a one turn circle in .134 s. What is the magnitude of the average induced emf in the wire during this time in units of V?