An electric resistor is a fundamental passive electrical component that opposes the flow of current in a circuit, thereby controlling voltage and current levels. It functions based on Ohm’s Law, where resistance (R) is measured in ohms (Ω), and the relationship is given by V = I × R, with voltage (V) in volts and current (I) in amperes.
Resistors are categorized into types such as fixed resistors (e.g., carbon film, metal film), which maintain a constant value, and variable resistors (e.g., potentiometers, rheostats), which allow adjustment. Key specifications include resistance value, power rating (watts), tolerance (percentage accuracy), and temperature coefficient.
Common applications include limiting current in LED circuits, dividing voltages in signal processing, providing bias in transistors, and acting as loads in power supplies. Resistors also play roles in sensors like thermistors (temperature-dependent) and photodetectors.
In circuit design, resistors help manage heat dissipation, prevent short circuits, and ensure stability, making them essential in electronics from simple devices to complex systems like computers and telecommunications equipment.
Table of contents
- Part 1: OnlineExamMaker AI quiz generator – The easiest way to make quizzes online
- Part 2: 20 electric resistor quiz questions & answers
- Part 3: OnlineExamMaker AI Question Generator: Generate questions for any topic
Part 1: OnlineExamMaker AI quiz generator – The easiest way to make quizzes online
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Part 2: 20 electric resistor quiz questions & answers
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1. Question: What is the unit of electrical resistance?
A. Ampere
B. Volt
C. Ohm
D. Watt
Answer: C
Explanation: The unit of electrical resistance is the ohm, defined as the resistance between two points of a conductor when a constant potential difference of one volt produces a current of one ampere.
2. Question: According to Ohm’s Law, what is the relationship between voltage (V), current (I), and resistance (R)?
A. V = I + R
B. V = I * R
C. V = I / R
D. V = R – I
Answer: B
Explanation: Ohm’s Law states that voltage equals current multiplied by resistance (V = I * R), describing how resistance affects the flow of current in a circuit.
3. Question: In a series circuit with two resistors of 2 ohms and 4 ohms, what is the total resistance?
A. 2 ohms
B. 4 ohms
C. 6 ohms
D. 8 ohms
Answer: C
Explanation: In a series circuit, total resistance is the sum of individual resistances, so 2 ohms + 4 ohms = 6 ohms.
4. Question: In a parallel circuit with two resistors of 2 ohms and 4 ohms, what is the total resistance?
A. 1.33 ohms
B. 2 ohms
C. 4 ohms
D. 6 ohms
Answer: A
Explanation: For parallel resistors, total resistance is calculated as 1/R_total = 1/2 + 1/4 = 0.75, so R_total = 1 / 0.75 = 1.33 ohms.
5. Question: What does the first color band on a resistor represent?
A. Multiplier
B. Tolerance
C. First digit
D. Temperature coefficient
Answer: C
Explanation: The first color band on a resistor represents the first significant digit of its resistance value.
6. Question: If a 5 ohm resistor carries a current of 2 amperes, what is the voltage across it?
A. 2.5 volts
B. 5 volts
C. 7 volts
D. 10 volts
Answer: D
Explanation: Using Ohm’s Law, V = I * R = 2 amperes * 5 ohms = 10 volts.
7. Question: What is the power dissipated by a 10 ohm resistor with 5 volts across it?
A. 0.5 watts
B. 2.5 watts
C. 5 watts
D. 10 watts
Answer: B
Explanation: Power is calculated as P = V^2 / R = (5 volts)^2 / 10 ohms = 25 / 10 = 2.5 watts.
8. Question: In a series circuit, how does adding more resistors affect the total current?
A. Increases it
B. Decreases it
C. Keeps it the same
D. Doubles it
Answer: B
Explanation: In a series circuit, total resistance increases with more resistors, which decreases the total current for a fixed voltage, as per Ohm’s Law.
9. Question: What is the equivalent resistance of three 6 ohm resistors in parallel?
A. 2 ohms
B. 6 ohms
C. 12 ohms
D. 18 ohms
Answer: A
Explanation: For three identical resistors in parallel, 1/R_total = 1/6 + 1/6 + 1/6 = 3/6 = 0.5, so R_total = 1 / 0.5 = 2 ohms.
10. Question: A resistor has color bands: brown, black, red, and gold. What is its resistance?
A. 10 ohms
B. 100 ohms
C. 1,000 ohms
D. 10,000 ohms
Answer: C
Explanation: Brown (1), black (0), red (multiplier of 100), so resistance is 10 * 100 = 1,000 ohms, with gold indicating 5% tolerance.
11. Question: What happens to the current in a parallel circuit if one resistor fails open?
A. Current increases
B. Current decreases in that branch only
C. Total current remains the same
D. Total current stops
Answer: B
Explanation: In a parallel circuit, if one resistor fails open, current stops in that branch, but the other branches continue to operate normally.
12. Question: For a voltage divider with two 1k ohm resistors in series, what is the output voltage if input is 10 volts?
A. 2.5 volts
B. 5 volts
C. 7.5 volts
D. 10 volts
Answer: B
Explanation: The voltage divides equally, so output across the second resistor is 10 volts / 2 = 5 volts.
13. Question: What is the tolerance of a resistor with a silver band?
A. 1%
B. 5%
C. 10%
D. 20%
Answer: C
Explanation: A silver band indicates a tolerance of 10%, meaning the actual resistance can vary by ±10% from the stated value.
14. Question: In a circuit with 12 volts and two resistors (3 ohms and 6 ohms) in series, what is the voltage across the 6 ohm resistor?
A. 4 volts
B. 6 volts
C. 8 volts
D. 12 volts
Answer: C
Explanation: Total resistance is 9 ohms. Current is 12V / 9 ohms = 1.33A. Voltage across 6 ohms is 1.33A * 6 ohms = 8 volts.
15. Question: What type of resistor changes value based on light exposure?
A. Thermistor
B. Photoresistor
C. Variable resistor
D. Carbon resistor
Answer: B
Explanation: A photoresistor, or LDR, varies its resistance based on the intensity of light falling on it.
16. Question: If two resistors of 4 ohms each are in parallel, what is their equivalent resistance?
A. 2 ohms
B. 4 ohms
C. 8 ohms
D. 16 ohms
Answer: A
Explanation: For two identical resistors in parallel, R_total = R/2 = 4 ohms / 2 = 2 ohms.
17. Question: What is the current through a 2 ohm resistor if the power dissipated is 8 watts?
A. 2 amperes
B. 4 amperes
C. 6 amperes
D. 8 amperes
Answer: A
Explanation: Power is P = I^2 * R, so 8 = I^2 * 2. Solving for I, I^2 = 4, so I = 2 amperes.
18. Question: In Kirchhoff’s Voltage Law, what is the sum of voltages around a closed loop?
A. Zero
B. Equal to current
C. Equal to resistance
D. Positive
Answer: A
Explanation: Kirchhoff’s Voltage Law states that the algebraic sum of all voltages around any closed loop in a circuit is zero.
19. Question: What is the resistance of a wire that has a voltage of 6 volts and carries 3 amperes?
A. 0.5 ohms
B. 1 ohm
C. 2 ohms
D. 3 ohms
Answer: C
Explanation: Using Ohm’s Law, R = V / I = 6 volts / 3 amperes = 2 ohms.
20. Question: A Wheatstone bridge is balanced when the ratio of resistances in one arm equals the ratio in the other. What is the condition for balance?
A. R1/R2 = R3/R4
B. R1 + R2 = R3 + R4
C. R1 * R2 = R3 * R4
D. R1 – R2 = R3 – R4
Answer: A
Explanation: For a Wheatstone bridge to be balanced, the condition is R1/R2 = R3/R4, resulting in zero current through the galvanometer.
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