Electric Circuits Answers

1. Assume that an RF amplifier’s input has a signal power of 2μW and a noise power of 323nW, what is the signal-to-noise ratio? (5 points)
2. Assume that the RF amplifier in problem number 1 has a signal-to-noise ratio of 5 at the output. Calculate the noise ratio and noise figure. (5 points)
3. Given the noise ratio calculated in problem number 2, what is its equivalent noise temperature? (5 points)
4. What is the average noise power of a device operating at temperature 75^oF with a bandwidth of 33 kHz? (10 points)

A 7.0 * 10^-9 C point charges at the center of a 5.0 cm radius sphear. What is the electric flux through the sphere surface?

Two unknown charges attract each other. The first charge has twice greater magnitude than the second charge. If the first acting under charge is 20^-12 N and the distance between them is 120 nm, what is the charge of the second charge? what is the force at 200 nm?

What is the relation b/w the frequency of applied voltage and natural frequency of the  circuit in a series resonant circuit?

An AC load exhibits a lagging power factor of 0.73 at 230 VAC and 315 amps. If the

system frequency is 60 Hz, calculate the following:

Apparent power (S) =?

A. 72.45 kVA B. 724.5 kVA C. 7.245 kVA

True power (P) =?

A. 5.289 kW B. 52.89 kW C. 528.9 kW

Reactive power (Q) =?

A. 4.952 kVAR B. 495.2 kVAR C. 49.52 kVAR

The electrical flux density between two plates separated by polystyrene of relative permittivity 2.5 is 5µ C/m2 . Find the voltage gradient between the plates. 

Flowing fluids, such as water, oil and air produce static charge why is it not as important to create static charge safety rules for handling flowing water as for handling air or oil?

. Two impedances Z1 and Z2 are connected in parallel. The first branch takes a leading current of 16 A and has a resistance of 5 Ω, while the second branch takes a lagging current at 0.8pf. The applied voltage is 100+j200 V and the total power is 5 kW. Find branch impedances, total circuit impedance, branch currents and total circuit current.

Draw the phasor diagram and find the sum of the currents: i₁=141.42Sin(ωt +  π/2) , i₂ = -70.71 Cos ωt , i₃= 50 e^j π/3 , i₄=100∠-2 π/3 and i₅= 50 (Cosπ/3 + j Sinπ/3) 

Two coils A and B are connected in series across a 110V, 60Hz supply. The resistance of coil A is 2Ω and inductance of coil B is 0.004H. If the input from the supply is 2.4kW and 1.8kVAR, find the inductance of coil A and resistance of coil B. Also calculate the voltage across each coil.