Q. If the resistances in a Wheatstone bridge are R1 = 10Ω, R2 = 20Ω, R3 = 15Ω, what should R4 be for the bridge to be balanced?
A.
30Ω
B.
15Ω
C.
20Ω
D.
10Ω
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Solution
Using the balance condition R1/R2 = R3/R4, we find R4 = (R2 * R3) / R1 = (20 * 15) / 10 = 30Ω.
Correct Answer: B — 15Ω
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Q. If the resistances in a Wheatstone bridge are R1 = 20Ω, R2 = 30Ω, and R3 = 10Ω, what is the value of R4 for the bridge to be balanced?
A.
15Ω
B.
20Ω
C.
25Ω
D.
30Ω
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Solution
Using the balance condition R1/R2 = R3/R4, we have 20/30 = 10/x, solving gives x = 20Ω.
Correct Answer: B — 20Ω
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Q. If the resistances in a Wheatstone bridge are R1, R2, R3, and R4, what is the condition for balance?
A.
R1/R2 = R3/R4
B.
R1 + R2 = R3 + R4
C.
R1 * R4 = R2 * R3
D.
R1 - R2 = R3 - R4
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Solution
The condition for balance in a Wheatstone bridge is R1/R2 = R3/R4.
Correct Answer: A — R1/R2 = R3/R4
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Q. If the resistivity of a material is 1.5 x 10^-8 Ω·m, what is the resistance of a 3 m long wire with a cross-sectional area of 0.5 mm²?
A.
0.09 Ω
B.
0.18 Ω
C.
0.27 Ω
D.
0.36 Ω
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Solution
Resistance R = ρ(L/A) = (1.5 x 10^-8)(3)/(0.5 x 10^-6) = 0.09 Ω.
Correct Answer: B — 0.18 Ω
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Q. If the resistivity of a material is 2 x 10^-8 Ω·m and the wire has a length of 3 m and a cross-sectional area of 0.5 mm², what is the resistance?
A.
0.12 Ω
B.
0.15 Ω
C.
0.18 Ω
D.
0.20 Ω
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Solution
Resistance R = ρ * (L / A) = 2 x 10^-8 * (3 / 0.5 x 10^-6) = 0.12 Ω.
Correct Answer: A — 0.12 Ω
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Q. If the resistivity of a material is doubled, what happens to the resistance of a wire of fixed length and cross-sectional area?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
Resistance R is directly proportional to resistivity; if resistivity doubles, resistance also doubles.
Correct Answer: A — It doubles
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Q. If the resistivity of a material is doubled, what happens to the resistance of a wire of constant length and cross-sectional area?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
Resistance R is directly proportional to resistivity ρ, so if ρ is doubled, R also doubles.
Correct Answer: A — It doubles
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Q. If the resistivity of a material is halved, what happens to the resistance of a uniform wire of that material?
A.
Halved
B.
Doubled
C.
Remains the same
D.
Quadrupled
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Solution
Resistance is directly proportional to resistivity; halving resistivity halves the resistance.
Correct Answer: A — Halved
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Q. If the resistivity of a material is halved, what happens to the resistance of a wire of fixed length and cross-sectional area?
A.
Halved
B.
Doubled
C.
Remains the same
D.
Quadrupled
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Solution
Resistance is directly proportional to resistivity; halving resistivity halves the resistance.
Correct Answer: A — Halved
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Q. If the resistivity of a material is halved, what will happen to the resistance of a wire of fixed length and cross-sectional area?
A.
Halved
B.
Doubled
C.
Remains the same
D.
Quadrupled
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Solution
Resistance is directly proportional to resistivity; halving resistivity halves the resistance.
Correct Answer: A — Halved
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Q. If the resistivity of a superconductor is zero, what can be said about its resistance?
A.
Infinite
B.
Zero
C.
Depends on temperature
D.
Undefined
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Solution
A superconductor has zero resistivity, which means it has zero resistance.
Correct Answer: B — Zero
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Q. If the resistivity of copper is 1.68 x 10^-8 Ω·m, what is the resistance of a copper wire of length 100 m and diameter 1 mm?
A.
0.168 Ω
B.
0.168 kΩ
C.
1.68 Ω
D.
1.68 kΩ
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Solution
Resistance R = ρ * (L / A) = 1.68 x 10^-8 * (100 / (π * (0.5 x 10^-3)²)) = 0.168 Ω.
Correct Answer: A — 0.168 Ω
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Q. If the RMS speed of a gas is 250 m/s, what is the temperature if the molar mass is 0.028 kg/mol?
A.
100 K
B.
200 K
C.
300 K
D.
400 K
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Solution
Using v_rms = sqrt(3RT/M), we can rearrange to find T = (v_rms^2 * M) / (3R) = 300 K.
Correct Answer: C — 300 K
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Q. If the RMS speed of a gas is 300 m/s and its molar mass is 28 g/mol, what is the temperature of the gas?
A.
300 K
B.
600 K
C.
900 K
D.
1200 K
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Solution
Using the formula v_rms = sqrt((3RT)/M), we can rearrange to find T = (v_rms^2 * M)/(3R). Plugging in the values gives T = 600 K.
Correct Answer: B — 600 K
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Q. If the RMS speed of a gas is 300 m/s at 300 K, what will be its RMS speed at 600 K?
A.
300 m/s
B.
600 m/s
C.
300√2 m/s
D.
600√2 m/s
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Solution
The RMS speed is proportional to the square root of the temperature. Therefore, at 600 K, the RMS speed will be 300 * sqrt(2) m/s.
Correct Answer: C — 300√2 m/s
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Q. If the RMS speed of a gas is 300 m/s at 400 K, what will be the RMS speed at 200 K?
A.
150 m/s
B.
300 m/s
C.
600 m/s
D.
100 m/s
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Solution
The RMS speed is proportional to the square root of the temperature. Therefore, at 200 K, the RMS speed will be 300 * sqrt(200/400) = 150 m/s.
Correct Answer: A — 150 m/s
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Q. If the RMS speed of a gas is 300 m/s at 400 K, what will be the RMS speed at 800 K?
A.
300 m/s
B.
600 m/s
C.
424 m/s
D.
848 m/s
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Solution
RMS speed is proportional to the square root of temperature. v_rms at 800 K = 300 * sqrt(800/400) = 300 * sqrt(2) = 600 m/s.
Correct Answer: B — 600 m/s
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Q. If the RMS speed of a gas is 300 m/s, what is the kinetic energy per molecule?
A.
0.5 * m * (300)^2
B.
0.5 * m * (150)^2
C.
0.5 * m * (600)^2
D.
0.5 * m * (100)^2
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Solution
The kinetic energy per molecule is given by KE = 0.5 * m * v^2. Substituting v = 300 m/s gives the correct expression.
Correct Answer: A — 0.5 * m * (300)^2
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Q. If the RMS speed of a gas is 300 m/s, what is the RMS speed of the same gas at double the temperature?
A.
300 m/s
B.
600 m/s
C.
300√2 m/s
D.
600√2 m/s
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Solution
The RMS speed is proportional to the square root of the temperature. If the temperature is doubled, the RMS speed increases by a factor of sqrt(2). Therefore, the new RMS speed will be 300 * sqrt(2), which is approximately 600 m/s.
Correct Answer: B — 600 m/s
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Q. If the RMS speed of a gas is 400 m/s and its molar mass is 16 g/mol, what is the temperature of the gas?
A.
200 K
B.
400 K
C.
800 K
D.
1600 K
Show solution
Solution
Using the formula v_rms = sqrt((3RT)/M), we can rearrange to find T: T = (M * v_rms^2) / (3R). Substituting M = 0.016 kg/mol and v_rms = 400 m/s gives T = 400 K.
Correct Answer: B — 400 K
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Q. If the RMS speed of a gas is 400 m/s at 300 K, what will be the RMS speed at 600 K?
A.
400 m/s
B.
800 m/s
C.
400√2 m/s
D.
800√2 m/s
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Solution
The RMS speed increases with the square root of the temperature. Therefore, at 600 K, the RMS speed will be 400 * sqrt(2), which is approximately 800 m/s.
Correct Answer: B — 800 m/s
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Q. If the RMS speed of a gas is 400 m/s, what is the kinetic energy per molecule at 300 K?
A.
0.5 mJ
B.
0.4 mJ
C.
0.2 mJ
D.
0.1 mJ
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Solution
Kinetic energy per molecule = (1/2)mv^2. Using v = 400 m/s and m = M/N_A, we find KE = 0.5 mJ.
Correct Answer: A — 0.5 mJ
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Q. If the RMS speed of a gas is 400 m/s, what is the speed of the gas molecules in terms of average speed?
A.
400 m/s
B.
300 m/s
C.
500 m/s
D.
600 m/s
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Solution
The average speed is related to RMS speed by the relation v_avg = (2/3) * v_rms. Thus, v_avg = (2/3) * 400 = 267 m/s.
Correct Answer: B — 300 m/s
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Q. If the RMS speed of a gas is 400 m/s, what is the speed of the molecules in terms of average speed?
A.
400 m/s
B.
300 m/s
C.
500 m/s
D.
600 m/s
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Solution
The average speed of gas molecules is approximately 0.8 times the RMS speed, so average speed = 0.8 * 400 m/s = 320 m/s.
Correct Answer: B — 300 m/s
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Q. If the RMS speed of a gas is 500 m/s, what is the speed of the gas molecules at 1/2 of the RMS speed?
A.
250 m/s
B.
500 m/s
C.
1000 m/s
D.
125 m/s
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Solution
The speed at 1/2 of the RMS speed is simply 500 m/s / 2 = 250 m/s.
Correct Answer: A — 250 m/s
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Q. If the RMS speed of a gas is 500 m/s, what is the speed of the gas molecules in terms of average speed?
A.
500 m/s
B.
250 m/s
C.
400 m/s
D.
600 m/s
Show solution
Solution
The average speed of gas molecules is related to the RMS speed by the relation v_avg = (v_rms * sqrt(8/3)). Therefore, the average speed is approximately 400 m/s.
Correct Answer: C — 400 m/s
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Q. If the RMS speed of a gas is 500 m/s, what is the speed of the molecules in the gas?
A.
500 m/s
B.
250 m/s
C.
1000 m/s
D.
It varies
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Solution
The RMS speed is an average measure; individual molecular speeds will vary around this value.
Correct Answer: D — It varies
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Q. If the RMS speed of a gas is 500 m/s, what is the temperature if the molar mass is 0.028 kg/mol?
A.
200 K
B.
300 K
C.
400 K
D.
500 K
Show solution
Solution
Using v_rms = sqrt(3RT/M), we rearrange to find T = (v_rms^2 * M) / (3R). Plugging in values gives T approximately 300 K.
Correct Answer: B — 300 K
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Q. If the roots of the equation ax^2 + bx + c = 0 are 3 and -2, what is the value of a if b = 5 and c = -6?
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Solution
Using Vieta's formulas, a = 1 since the product of the roots (3 * -2) = -6 and sum (3 + -2) = 1.
Correct Answer: A — 1
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Q. If the roots of the equation ax^2 + bx + c = 0 are 3 and -2, what is the value of b if a = 1 and c = -6?
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Solution
Using the sum of roots (-b/a = 3 + (-2) = 1), we find b = -1.
Correct Answer: A — -1
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