Electric Circuits Answers

a) How much would it cost to run a 60 W bulb for 1 month if energy costs $0.15 per kWh?

b) Assume the current density is uniform (equal density) across the cross section of a wire with radius r=8 cm. Suppose that the total current flow is I=4A. What is the current density?

a) How much current does your laptop consume if 100 C of charge is transferred through the charger wire in 4 seconds? 

b) How much time is required for a 20 Coulombs charge to flow through a point if the current is 2 amperes? 

a) A wire of a certain length (a=0.0065/°C) has a resistance of 4Ω (at 20°C). Find its resistance at 80°C.

a) A direct current generator of 127V provides 2.9kW to an electric oven. Determine the current it provides. Find the resistance. 

b) A wire 2 mm diameter and 100 m length has a resistance of 3Ω (at 20°C). Find its resistivity.

a) If a charge of 1000 Coulombs flows across a given point in 2 seconds, find the electric current in amperes.

b) Determine the emf required so that 13 mA can pass through a resistor of 200Ω. If that same emf is applied to a resistor of 1kΩ, find the new current.

Resistors in series and parallel

In a series connection solve for the total capacitance.

C1 = 3.5 x 10^-12 F

C2 = 2.41 x 10^-12 F

C3 = 1.13 x 10^-12 F

V = 1700 V

Determine the current flowing through an element if the charge flow is given by a. q(t)= (3e-t -5e-2t) nC b. q(t)= 10sin120πt pC c. q(t)= 20e-4tcos50t µC

1.       The maximum frequency deviation of the carrier is ± 15 kHz and the maximum modulating frequency is 3 kHz, calculate for the modulation index.

2.       Assume that the 60-dB bandwidth of a receiver is 12 kHz and the 6-dB bandwidth is 7 kHz. What is the shape factor of the circuit?

3.       What is the bandwidth of a receiver with a quality factor of 50 and a resonance frequency of 540 kHz.

4.       What is the maximum bandwidth of an FM signal with a deviation of 27 kHz and a maximum modulating signal of 4 kHz as determined by Carson’s rule?

5.       A PM signal has a maximum allowed deviation of 17 kHz and an actual deviation of 8 kHz. What is the percentage modulation?

1. There are stations having the maximum frequency deviation of 75 kHz, and the maximum audio frequency for the modulation is 15 kHz , find its deviation ratio.
2. Determine the peak frequency deviation for a FM modulator with a deviation sensitivity of 12 kHz/V  and a peak modulating signal of 9V.
3. If the maximum frequency deviation of the carrier is 10 kHz and the maximum modulating frequency is 6.7 kHz, find the modulating index.
4. A PM signal has a maximum allowed deviation of 22 kHz  and an actual deviation of 5 kHz . What is its percent modulation?