Electric Circuits Answers

Define a uniform electric field (E), and derive its work done in a moving charge (q) through a

distance (d)?

Consider two ohmic resistors denoted R1 and R2 which are connected in series with a

cell. Find the resistance and power of R2, given that the current flowing

through R1 and R2 is 0.25 A and that the voltage across the cell is 6 V. R1 = 1Ω.

A twenty-five volt battery, an ammeter, and a 5 ohm resistor are connected in series. Assume the resistor obeys Ohm’s law. There could be other circuit elements in the circuit. If the ammeter reads 1.9 A, are there other elements in the circuit? If so, what are they? Explain your reasoning using Kirchoff’s Laws and draw the circuit in the space below.

1. Calculate the wavelength of a waveform given a period of 17μs.

1. Given a dc bias of 0.5mA and a bandwidth of 10 kHz, calculate for the noise current.

1. Calculate the wavelength of a waveform given a period of 17μs.
2. Find the input thermal noise voltage of a receiver with a bandwidth of 3.33 kHz, with an input resistance of 42 Ω, and a temperature of 29^oC.
3. Given the signal power of 2.3 μW and the noise power of 0.7 μW, calculate the signal-to-noise ratio.
4. Three (3) AM broadcast stations are spaced at 18 kHz, beginning at 73 kHz. Each station is allowed to transmit modulating up to 6 kHz. Compute for the upper and lower sidebands of each station.
5. Given a dc bias of 0.5mA and a bandwidth of 10 kHz, calculate for the noise current.

Question

The output characteristics of a transistor in common-emitter configuration can be regarded as straight lines connecting the following points

   IB =     20 µA        50 µA          80 µA       

VCE(V) 1.0 8.0 1.0 8.0 1.0 8.0

IC (mA) 1.2 1.4 3.4 4.2 6.1 8.1

Plot the characteristics and superimpose the load line for a 1 kΩ load, given that the supply voltage is 9V and the d.c. base bias is 50 μA. The signal input resistance is 800 Ω. When a peak input current of 30 μA varies sinusoidally about a mean bias of 50 μA, determine

(a) The quiescent collector current 

(b) The current gain 

(c) The voltage gain

(d) The power gain

1. ssuming that an oscilloscope displays a V_max of 5.22V and V_min of 1.33V. Calculate the percentage of modulation. (5 points)
2. Three (3) AM broadcast stations are spaced at 18 kHz, beginning at 73 kHz. Each station is allowed to transmit modulating up to 6 kHz. Compute for the upper and lower sidebands of each station and plot it in the frequency domain. (15 points)
3. Given a V_max of 7.45V and a modulation index of 0.691, calculate for V_min. (5 points)
4. A station is given a carrier frequency of 88 kHz. Having a modulating frequency of 12 kHz, compute for the upper and lower sidebands of the station. (5 points)