Electrical Engineering Answers

Two coils A and B are wound on same iron core. There are 500 turns on coil A and 3000 turns on coil B. A current of 5A through coil A produces a flux of 600x10 wb in core. If

this current is reversed in 0.02sec, claculate average e.m.f. Induced in coils A and B.

A microwave detector is being used to measure the velocity of a vehicle driving normally to the face of the detector. The microwave detector has the following properties and inputs: Frequency f0 = 24.15 GHz Doppler frequency shift = 50 Hz S = 0.5 mV/g How fast is the vehicle going in meters/sec?

An accelerometer has the following properties:

Stiffness k = 500,000 N/m

Mass m = .01 Kg

Damping coefficient c = 95 N-sec/m

What is the damping ratio of the accelerometer?

A platinum wire has Poisson’s ratio ν = 0.39, and resistivity ρ of 1.06 x 10-7 ohm-meter. When the wire is pulled, the axial strain εA is 0.08 and the resistivity increases to 1.07 x 10-7 ohm-meter. What is the gauge factor of the platinum wire? (

A coil with resistance ‘

6

’

Ω

,

and

inductance

‘

8

’ mH

is connected

in parallel

with a

series

combination of

a

resist

or and

capacitor

having

resistance R

Ω and

reactance X

c

Ω.

If

t

he equivalent

impedance

of the resulting circuit is

Z =

5

/0

o

Ω at

ω

=1000 rad/sec

. Find the

values of R & C

.

The resistivity and temperature coefficient of resistance of Evanohm are 800 CM-Ω/ft and

20 x 10-6 /C, respectively, at 20C. A #40 round wire has a diameter of 0.00314 in. Find the resistance of a 14.79 in long sample of a #40 round Evanohm wire at (a) 20C, and

(b) 520C.

Analyze the signal H(t) = 5e^t U(t) This signal is discretized at a sampling frequency of 1kHz.

a)What is the expression for the discrete-time signal in n-domain?

b)Is this discrete-time signal periodic or aperiodic ? If it is periodic, find its period.

c) Find the spectrum of the discrete-time signal using Discrete-Time Fourier Transform.

d) Plot magnitude spectrum for at least two periods. You can use Matlab to plot it.

e)Find the Z-transform along with the Region of Convergence of this discrete-time signal.

How many operating forces are necessary for successful operation of an indicating instrument? Explain the methods of providing these forces.

How can the current range of a PMMC instrument be extended with the help of shunts?