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# EMF

### EMF induced in a conductor moving in a magnetic field.

EMF in a Bullet. At the equator, the earth's magnetic field is approximately horizontal and is directed toward the north and has a value of X. Part A Estimate the emf induced between the top and bottom of a bullet shot horizontally at a target on the equator if the bullet is shot toward the east. Assume the bullet has a len

### Find the current in the bulb

In the circuit of the figure attached, each resistor represents a light bulb. Let R_1=R_2=R_3=R_4= 4.27 ohms and let the EMF be 9.00 V. 1) Find the current in the bulb R_2: 2) Find the current in the bulb R_3: 3) Find the current in the bulb R_4:

### Current as a Function of Time for a Circuit

Let us now consider a different RC circuit. This time, the capacitor is initially charged (q(t) = q_0), and there is no source of EMF in the circuit. We will assume that the top plate of the capacitor initially holds positive charge. For this circuit, Kirchoff's loop rule gives IR + q/C = 0, or IR = -q/C. Find the current

### Time for capacitor charge to reach 99.9% maximum

Consider a series circuit containing a resistor of resistance R and a capacitor of capacitance C connected to a source of EMF E with negligible internal resistance. The wires are also assumed to have zero resistance. Initially, the switch is open and the capacitor discharged. Let us try to understand the processes that take

### Electromagnetic Induction and induced EMF

Magnetic resonance imaging (MRI) is a medical technique for producing pictures of the interior of the body. The patient is placed within a strong magnetic field. One safety concern is what would happen to the positively and negatively charged particles in the body fluids if an equipment failure caused the magnetic field to be sh

### output EMF of a generator

(See attached file for full problem description) 4. The drawing below shows a plot of the output emf of a generator as a function of time t. The coil of this device has a cross-secontal area per turn of 0.040 m2 and contains 136 turns. Find a. the frequency of the generator in Herz b. the angular speed in rad/s c. the magnit

### Capacity, charge and voltage

The radii of curvature of the spheres of a spherical capacitor is given and to find the charge, charge density and work done when it is connected to a battery. See attached file for full problem description.

### Inductance of a Solenoid

A long solenoid of length 8m with a cross-sectional area of 5.0x10^-5 m^2 contains 52,000 turns. 1) Find the self-inductance of the solenoid, assuming that the core is air. 2) If the current in the winding starts at 0 A and is increased steadily to 1.5 A in a time of 0.20 sec, what is the EMF induced in the solenoid?

### Faraday's Laws of Electromagnetic Induction

A coil of wire with 40 turns is held stationary between the poles of an electromagnet. The field in the electromagnet is increased from 0 to 0.75T in a time of 225 seconds. What is the magnitude of the induced EMF in the coil if the angle that the plane of the coil makes with the field is 30 degrees?

### Induced emf on a rotating rod in a uniform magnetic field

A uniform rod of length l is rotating with angular velocity w around the axis passing through the rod end and parallel to the field line of uniform magnetic field B. Derive an expression for potential difference across the rod. (For diagram please see the JPG file)

### Assorted Problem Set on Currents

See the attached file. 1. a) The magnitude of the earth's magnetic field at the surface of the earth is slightly less than one gauss.( I answered False and the answer was true) b) The torque exerted on a current loop by a uniform field tends to orient the plane of the loop perpendicular to the magnetic field.(I answered fals

### RL Circuits: Growth and decay of current in inductor

See attached circuit. Note current source is 2A,Resistors are 2 Ohms, Inductor 2H. Assume that the switch has been open for a long time and that it closes at t=0 sec. The switch remains closed thereafter. How do I solve for Vx(t) and Ix(t)?

### Current Electricity:Variable voltage, current in L, C and R

Determine and plot as a function of time the current through a component if the voltage across it has the waveform shown in Figure and the component is a: a) Resistor R = 7 &#937; b) Capacitor C = 0.5 &#956;F c) Inductor L = 7 mH

### Electromagnetic Induction: EMF in a ring outside a solenoid

A long solenoid is wound with 500 turns per meter and current in its windings is increasing at the rate of 100A/s. The Cross-sectional area of the solenoid is 4.0cm^2. If the solenoid is encircled at its center by a circular conducting loop, Find the magnitude of the induced electric field within the outside conduction loop if

### 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.

### 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

### 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

### 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?

### 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?

### 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