Electricity and Magnetism Answers

If a current carrying conductor with length L is hanging between the poles of a magnet as shown below. Find the magnitude and direction of force applied on the wire if the current I is flowing to the left. (Hint the magnetic field line is into the page.)

The strength of the homogeneous magnetic field was measured by the following experimental arrangement:  The rectangular conductor loop was partially introduced into the magnetic field as shown. The wire loop was hung on a computer power sensor and calibrated to show zero. When the current in the conductor loop was 325 mA, the force sensor showed a reading of 32.9 mN. Based on this, what was the magnetic flux density of the magnetic field? The magnetic field at the current loop was approximately homogeneous.

Given f=50Hz, determine how long it will take the sinusoidal waveform to pass through an angle of 50o

A 10 F capacitor is connected through a 1 M resistor to a constant potential difference of 100

V. Compute (a) the charge at time 5s (b) the current in the same instant (c) the time require for the

charge to increase from zero to 5×10-04 C (d) the final charge in the circuit (e) the relaxation time

and half-life of the circuit. (f) the time require for the charge to increase from 5×10-04 C to 7×10-04

C.

What do you understand by half-wave rectification of half-wave rectification of an alternating current? Obtain the following values of half-wave rectified A.C.

a)     RMS value

b)     Average value 

DESCRIBE the following:

a)     Dynamically induced emf

b)     Mutually induced emf

c)     Self-induced emf and its method

APPLY the concept to find the direction of induced emf and current by

a)     Fleming’s right hand

b)     Lenz’s law 

A beam of protons, each of which has mass m, and charge qe moving with a velocity V enters perpendicularly a uniform magnetic field with the magnitude B= 2uT directed into plane of the page. After the beam exits the magnetic field, leaving the field in a direction perpendicular to its original direction, the beam enters a uniform electric field with the intensity E = 2.10-8 V/m directed downward existing above a distance d=10 m. The beam travels a distance of 6 cm in the magnetic field. After the proton beam exits the magnetic field, what will be passing time till the proton beam stops in the electric field? (Neglect the effect of gravitation).

The small box provided contains a cell of emf

E

and internal resistance

r

. Using this cell, an ammeter

(with negligible resistance), a variable (but known) resistance (

R

) and a plug key connect the circuit as

shown below.

Note

the meter polarity.

(a)

Does it matter in what order the components are connected? Explain.

(b)

In this experiment

I

is the dependent and

R

is the independent variable. Is this correct? Explain.

(c)

(d)

1

1

r

R

I





E

E

Write down the equation for

E

in terms of the current,

I

, the external resistance,

R

, and the

internal resistance of the cell,

r

.

(E2.1)

Show that equation (E2.1) can be rearranged into a form suitable for plotting a straight-line

graph: