Tutorial 1 – Fundamentals of Electrical Circuits
TUTORIAL 1
FUNDAMENTALS OF ELECTRICAL CIRCUITS
1. Using Ohm’s Law, find the value of the quantity omitted across each line of the following table.
V / I / R64V / 16Ω
1.5A / 23 Ω
9V / 0.36A
36V / 25 kΩ
120V / 1.5MΩ
8mA / 4.7kΩ
3.8V / 76µA
450mV / 0.03kΩ
0.2kV / 800mA
5200pA / 1.85MΩ
2. The current in an electric heater is 0.6A when it is plugged into a 120V source. What is the resistance of the heater? What current would flow in the heater if the voltage dropped by 10%?
3. The resistance of an electronic component changes from 860Ω to 1.5kΩ when its temperature changes over a certain range. If it is desired to maintain 30mA of current in the component at all times, what range of voltages must a voltage source connected to it be capable of providing?
4.What is the voltage across a 1.2MΩ resistor if 4.5µC of charge passes through it in 30ms?
5.
How would you configure this circuit to measure the current through the resistor, and the voltage across the resistor? Explain how and why you would use red and black cables for this purpose.
6.If electrical energy costs £0.15/kWh, for how many 24 hour days can a 5W night light be operated without the cost exceeding £1.00?
7. Carbon-composite resistors are available with power ratings of 1/8, ¼, ½, 1, and 2W. Given the circuit values of voltage, current, and/or resistance in each of the following, determine the minimum power rating that the carbon-composition resistor can have.
a) R = 510Ω, V = 10V
b) R = 470Ω, I = 1.95mA
c) R = 3.3kΩ, V = 50V
d) V = 50mV, I = 0.2mA
8. A particular design requires that the current in a circuit be 3.45mA. A 12V source provides the current.
a) Find the closest standard value resistor with a 5% tolerance whose nominal value would limit the current to the required value ±10%.
b) Find the maximum percent deviation from 3.45mA that could result from using the standard value found in part (a).
9. Derive an expression for the power dissipated in a resistor in terms of its conductance G and
a) The current I through it.
b) The voltage V across it.
10. What range of terminal voltages would be developed by an ideal 12mA current source when a potentiometer that ranges from 50Ω to 5kΩ and a tolerance of ±10 is connected across its terminals?
11. On the voltage versus current graph of a 10kΩ resistor, what is the total change in voltage when the current changes from 1mA to 5.5mA?
12. Use Kirchhoff’s voltage law to find Vab in each circuit shown below.
13. Use the voltage divider rule to find voltage Vxy in each circuit shown below.
14. Use Kirchhoff’s current law to find the unknown current(s) in each part of the figure below. Draw an arrow on each diagram to show the positive direction of each current.
15. Use the current divider rule to find currents I1 and I2 in each of the circuits below.
EE1404 Circuit Theory1 of 3
Dr. Daniel Nankoo