Explore BrainMass


Batteries and Hydrogen

1. The lead acid battery used in cars uses the reaction of Pb + PbO2 + 2H+ + 2HSO4- ---> 2PbSO4 + 2H2O and has a cell potential of 2.046 volts. How are 6 volt and 12 volt batteries produced for cars? a. The pH is made very acidic. b. 3 or 6 cells are connected together to increase the voltage c. The concentrati

Potential of Cell

What is the potential of the following cell: Pt|H2(g)|(H+, pH=3)||(H+, pH=7)|H2(g)|Pt

Introduction to Decision Making

You are observing a meeting between Milhouse (one of your co-workers) and a salesman who is trying to sell an additional part to a machine that your company recently purchased. The salesman is well into his routine, and has already gotten your co-worker to admit that a quality product is of utmost importance to the future of the

Induced emf coils

A coil with a self-inductance of 0.750 mH experiences a constant current buildup from zero to 10 amperes in 0.250 seconds. What is the induced emf during this interval?

A problem on speed control of DC motor.

A separately excited dc motor is running at 500rpm, driving a load whose torque is proportional to the speed, the motor armature voltage is 220V and the armature current is 20A. What resistance should be inserted in the armature circuit to reduce the motor speed to 250rpm? The armature resistance is 1 ohm.

Looking for help with image formats

What kinds of image formats are available for putting onto the Internet? What different file formats that are available to me? What are the major advantages and disadvantages of each one?

Induced emf in loop.

The current in the long straight wire AB of the figure is upward and is increasing steadily at a rate of di/dt. 1. what is the total flux in through the loop? 2. what is the induced emf in the loop?

Induced EMF in a circular loop

A circular loop of flexible iron wire has an initial circumference of 165.0 cm, but its circumference is decreasing at a constant rate of 12.0 cm/s due to a tangential pull on the wire. The loop is in a constant uniform magnetic field of magnitude 0.500 T, which is oriented perpendicular to the plane of the loop. Find the in

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

EMF induced by train's axles

An engineer plans to light a train by utilizing the emf induced in the axles of the train running on the tracks. a. If the downward component of the earth's magnetic field is 0.6 X 10^-4 T, and the tracks are 1.5m apart, how large is the emf produced between the tracks by a train traveling at 40 m/s? b. Could this voltag

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?

Generators and Motors

A 50-turn loop of wire has a cross-sectional area of 0.010 m^2. It is rotated about an axis perpendicular to the earth's field of 5.0 × 10^-5 T. What is the peak value of the emf generated if the loop rotates at 3600 rotations per minute? I need to see each step and formula to solve this question. Please assume I know nothin

Faraday's laws of electromagnetic induction: Induced EMF.

A rectangular loop with an area of 120 cm^2 is placed in a magnetic field of 1.3 × 10^-2T and rotated about its long axis at 5.0 Hz. What is the instantaneous emf generated at the instant when the normal to the loop makes an angle θ = 0.27^o with the magnetic field?

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)

Electromagnetic Induction: Current in a rotating coil.

Consider a uniform, constant magnetic field pointing in the z-direction with a strength B_0. Put a square loop of wire with resistance R and side length l in the xy-plane at time t=o and spinning about the x-direction with a constant angular velocity omega. What is the current through the loop as a function of time?

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

Charging of a Capacitor

See the attached file. Determine vc(t) for t > 0. The voltage across the capacitor in Figure P5.32 (attached file) just before the switch is changed as shown in the attached file. vc(0-) = -7 V Io = 17 mA C = 0.55 μF R1 = 7 kΩ R2 = 3.3 kΩ See the attached file.

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)?

Growth of Current in Inductor: V-T Plot

The voltage across an inductor plotted as a function of time is shown in Figure (see attached file). If L = 0.75 mH, determine the current through the inductor at t = 15 mu s.