Q. If a charge Q is uniformly distributed over a sphere of radius R, what is the electric field at a distance r from the center where r > R?
A.
Q/(4πε₀r²)
B.
Q/(4πε₀R²)
C.
0
D.
Q/(4πε₀R²) * (R/r)²
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Solution
For r > R, the electric field behaves as if all the charge were concentrated at the center, given by E = Q/(4πε₀r²).
Correct Answer:
A
— Q/(4πε₀r²)
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Q. If a charge Q is uniformly distributed over a spherical surface of radius R, what is the electric field at a point inside the sphere?
A.
Q/(4πε₀R²)
B.
0
C.
Q/(4πε₀R)
D.
Q/(4πε₀R³)
Show solution
Solution
Inside a uniformly charged spherical shell, the electric field is zero.
Correct Answer:
B
— 0
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Q. If a charge Q is uniformly distributed over a spherical surface of radius R, what is the electric field at a point outside the sphere at a distance r from the center (r > R)?
A.
0
B.
Q/(4πε₀r²)
C.
Q/(4πε₀R²)
D.
Q/(4πε₀R)
Show solution
Solution
For a point outside the sphere, the electric field behaves as if all the charge were concentrated at the center, hence E = Q/(4πε₀r²).
Correct Answer:
B
— Q/(4πε₀r²)
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Q. If a child sitting on a merry-go-round moves closer to the center, what happens to the angular velocity of the merry-go-round?
A.
Increases
B.
Decreases
C.
Remains the same
D.
Becomes zero
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Solution
As the child moves closer, the moment of inertia decreases, and to conserve angular momentum, angular velocity must increase.
Correct Answer:
A
— Increases
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Q. If a child sitting on a merry-go-round moves from the center to the edge, what happens to the angular momentum of the system if no external torque acts?
A.
Increases
B.
Decreases
C.
Remains constant
D.
Becomes zero
Show solution
Solution
Angular momentum remains constant if no external torque acts, according to the conservation of angular momentum.
Correct Answer:
C
— Remains constant
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Q. If a child sitting on a merry-go-round moves towards the center, what happens to the angular velocity of the merry-go-round?
A.
Increases
B.
Decreases
C.
Remains the same
D.
Becomes zero
Show solution
Solution
As the child moves towards the center, the moment of inertia decreases, thus angular velocity increases to conserve angular momentum.
Correct Answer:
A
— Increases
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Q. If a chord of a circle is 16 cm long and is 6 cm away from the center, what is the radius of the circle?
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Solution
Using the formula: radius² = (distance from center to chord)² + (half of chord length)². Here, radius² = 6² + (16/2)² = 36 + 64 = 100, so radius = √100 = 10.
Correct Answer:
B
— 12
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Q. If a chord of a circle is 16 cm long and the radius is 10 cm, what is the distance from the center of the circle to the chord?
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Solution
Using the formula d = √(r^2 - (c/2)^2), where r = 10 and c = 16, we get d = √(10^2 - 8^2) = √(100 - 64) = √36 = 6.
Correct Answer:
B
— 8
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Q. If a circle has a circumference of 31.4 cm, what is its radius? (2022)
A.
5 cm
B.
10 cm
C.
15 cm
D.
20 cm
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Solution
Circumference = 2πr; 31.4 = 2 * π * r; r = 31.4 / (2 * π) = 5 cm.
Correct Answer:
A
— 5 cm
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Q. If a circle has a circumference of 62.8 cm, what is its diameter?
A.
10 cm
B.
20 cm
C.
30 cm
D.
40 cm
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Solution
Using the formula C = πd, we find d = C/π = 62.8/3.14 = 20 cm.
Correct Answer:
B
— 20 cm
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Q. If a circle has a circumference of 62.8 cm, what is its radius? (2018)
A.
10 cm
B.
20 cm
C.
15 cm
D.
5 cm
Show solution
Solution
Circumference = 2πr; 62.8 = 2 * π * r; r = 62.8 / (2 * π) = 10 cm.
Correct Answer:
A
— 10 cm
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Q. If a circle has a diameter of 10, what is its circumference?
A.
10π
B.
20π
C.
5π
D.
15π
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Solution
Circumference C = πd = π(10) = 10π.
Correct Answer:
B
— 20π
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Q. If a circle has a radius of 10 cm, what is the length of an arc that subtends a central angle of 90 degrees?
A.
15.7 cm
B.
25 cm
C.
17.5 cm
D.
20 cm
Show solution
Solution
The length of an arc is given by L = (θ/360) * 2πr. Here, L = (90/360) * 2π(10) = 17.5 cm.
Correct Answer:
C
— 17.5 cm
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Q. If a circle has a radius of 10 m, what is the diameter? (2021)
A.
5 m
B.
10 m
C.
20 m
D.
15 m
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Solution
Diameter = 2 * radius = 2 * 10 m = 20 m.
Correct Answer:
C
— 20 m
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Q. If a circle has a radius of 3 cm, what is its circumference? (Use π = 3.14) (2023)
A.
6.28 cm
B.
9.42 cm
C.
12.56 cm
D.
15.70 cm
Show solution
Solution
Circumference = 2πr = 2 * 3.14 * 3 = 18.84 cm.
Correct Answer:
C
— 12.56 cm
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Q. If a circle has a radius of 4 cm, what is its circumference? (Use π = 3.14) (2023)
A.
12.56 cm
B.
25.12 cm
C.
50.24 cm
D.
6.28 cm
Show solution
Solution
Circumference = 2πr = 2 * 3.14 * 4 cm = 25.12 cm.
Correct Answer:
A
— 12.56 cm
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Q. If a circle has a radius of 4 cm, what is its diameter? (2022)
A.
4 cm
B.
8 cm
C.
12 cm
D.
16 cm
Show solution
Solution
Diameter = 2 * radius = 2 * 4 cm = 8 cm.
Correct Answer:
B
— 8 cm
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Q. If a circle has a radius of 7 cm, what is its area? (2020)
A.
154 cm²
B.
49 cm²
C.
28 cm²
D.
14 cm²
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Solution
The area of a circle is calculated using A = πr². Thus, A = π(7)² = 49π ≈ 154 cm².
Correct Answer:
A
— 154 cm²
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Q. If a circle has a radius of 7 cm, what is its circumference?
A.
14π cm
B.
21π cm
C.
28π cm
D.
49π cm
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Solution
The circumference of a circle is given by 2πr. Here, r = 7 cm, so circumference = 2π * 7 = 14π cm.
Correct Answer:
B
— 21π cm
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Q. If a circle has a radius of 7 cm, what is its circumference? (Use π = 22/7)
A.
44 cm
B.
22 cm
C.
14 cm
D.
28 cm
Show solution
Solution
Circumference = 2πr = 2 × (22/7) × 7 = 44 cm.
Correct Answer:
A
— 44 cm
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Q. If a circle has a radius of 7 cm, what is its circumference? (Use π ≈ 3.14)
A.
21.98 cm
B.
43.96 cm
C.
14 cm
D.
28 cm
Show solution
Solution
Circumference = 2 * π * radius = 2 * 3.14 * 7 ≈ 43.96 cm.
Correct Answer:
B
— 43.96 cm
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Q. If a circle has a radius of 7 units, what is its area?
A.
154
B.
144
C.
100
D.
50
Show solution
Solution
Area = π * r^2 = π * 7^2 = 154 (using π ≈ 22/7).
Correct Answer:
A
— 154
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Q. If a circle has an area of 50π cm², what is its diameter? (2020)
A.
10 cm
B.
20 cm
C.
5 cm
D.
15 cm
Show solution
Solution
Area = πr², so r² = 50. Thus, r = √50 = 5√2 cm. Diameter = 2r = 10√2 cm ≈ 14.14 cm.
Correct Answer:
A
— 10 cm
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Q. If a circle has the equation x² + y² - 4x + 6y + 9 = 0, what is the center of the circle?
A.
(2, -3)
B.
(2, 3)
C.
(-2, 3)
D.
(-2, -3)
Show solution
Solution
Rearranging the equation to standard form gives (x - 2)² + (y + 3)² = 0, thus the center is (2, -3).
Correct Answer:
A
— (2, -3)
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Q. If a circle is centered at (0, 0) with a radius of 5, which of the following points lies outside the circle?
A.
(3, 4)
B.
(0, 5)
C.
(5, 0)
D.
(6, 0)
Show solution
Solution
The equation of the circle is x² + y² = 25. The point (6, 0) gives 6² + 0² = 36, which is greater than 25, hence it lies outside.
Correct Answer:
D
— (6, 0)
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Q. If a circle's radius is doubled, how does its area change? (2020)
A.
It remains the same
B.
It doubles
C.
It triples
D.
It quadruples
Show solution
Solution
Area = πr². If radius is doubled (2r), new area = π(2r)² = 4πr², which is quadruple the original area.
Correct Answer:
D
— It quadruples
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Q. If a circle's radius is tripled, by what factor does the area increase? (2019)
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Solution
Area = πr²; If r is tripled, new area = π(3r)² = 9πr²; Factor = 9.
Correct Answer:
D
— 9
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Q. If a circle's radius is tripled, how does its area change? (2021)
A.
Increases by 3 times
B.
Increases by 6 times
C.
Increases by 9 times
D.
Remains the same
Show solution
Solution
Area = πr². If radius is tripled, new area = π(3r)² = 9πr², which is 9 times the original area.
Correct Answer:
C
— Increases by 9 times
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Q. If a circle's radius is tripled, how does its area change? (2023) 2023
A.
Increases by 3 times
B.
Increases by 6 times
C.
Increases by 9 times
D.
Remains the same
Show solution
Solution
Area = πr². If radius is tripled, new area = π(3r)² = 9πr², which is 9 times the original area.
Correct Answer:
C
— Increases by 9 times
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Q. If a circuit contains a 12V battery and two resistors in series of 3Ω and 9Ω, what is the current flowing through the circuit?
A.
0.5A
B.
1A
C.
1.5A
D.
2A
Show solution
Solution
Total resistance R = R1 + R2 = 3Ω + 9Ω = 12Ω. Using Ohm's law, I = V/R = 12V/12Ω = 1A.
Correct Answer:
B
— 1A
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