Medical Entrance
Q. If the diameter of a wire is halved while keeping the length constant, what happens to its tensile strength? (2019)
A.
It doubles
B.
It halves
C.
It quadruples
D.
It remains the same
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Solution
Tensile strength is inversely proportional to the cross-sectional area. Halving the diameter reduces the area to a quarter, thus tensile strength quadruples.
Correct Answer: C — It quadruples
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Q. If the distance between the plates of a capacitor is halved, what happens to the capacitance? (2019)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
If the distance d is halved, the capacitance C = εA/d will double.
Correct Answer: A — It doubles
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Q. If the distance between two masses is doubled, what happens to the gravitational force between them? (2020)
A.
It doubles
B.
It halves
C.
It becomes one-fourth
D.
It becomes four times
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Solution
According to the inverse square law, if the distance is doubled, the force becomes 1/(2^2) = 1/4 of the original force.
Correct Answer: C — It becomes one-fourth
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Q. If the electric field between the plates of a capacitor is E, what is the potential difference between the plates separated by a distance d? (2020)
A.
E/d
B.
Ed
C.
d/E
D.
E*d
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Solution
The potential difference (V) between the plates is given by V = Ed, where E is the electric field and d is the distance between the plates.
Correct Answer: B — Ed
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Q. If the equilibrium constant Kc for a reaction is 10, what is the value of Kc for the reverse reaction? (2020)
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Solution
For the reverse reaction, Kc is the reciprocal of the forward reaction. Therefore, Kc (reverse) = 1/Kc (forward) = 1/10 = 0.1.
Correct Answer: A — 0.1
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Q. If the frequency of an AC source is 50 Hz, what is the time period of the AC signal? (2019)
A.
0.02 s
B.
0.01 s
C.
0.5 s
D.
1 s
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Solution
The time period (T) is the reciprocal of frequency (f). Therefore, T = 1/f = 1/50 Hz = 0.02 s.
Correct Answer: A — 0.02 s
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Q. If the inductance of a coil is doubled, what happens to its inductive reactance at a constant frequency? (2022)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
Inductive reactance (X_L) is given by X_L = 2πfL. If the inductance (L) is doubled, X_L will also double.
Correct Answer: A — It doubles
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Q. If the length of a wire is doubled while keeping the diameter constant, what happens to its resistance? (2019)
A.
It doubles
B.
It halves
C.
It quadruples
D.
It remains the same
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Solution
Resistance (R) is directly proportional to length (L). If length is doubled, resistance also doubles.
Correct Answer: A — It doubles
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Q. If the magnetic flux through a coil changes from 0.5 Wb to 0.2 Wb in 2 seconds, what is the average induced emf? (2023)
A.
150 V
B.
100 V
C.
75 V
D.
50 V
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Solution
Average induced emf = -ΔΦ/Δt = -(0.2 - 0.5)/2 = 0.15 V = 150 V.
Correct Answer: B — 100 V
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Q. If the potential difference across a capacitor is increased, what happens to the charge stored in it? (2020)
A.
It decreases
B.
It remains the same
C.
It increases
D.
It becomes zero
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Solution
The charge (Q) stored in a capacitor is directly proportional to the potential difference (V) across it, given by Q = CV.
Correct Answer: C — It increases
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Q. If the radius of curvature of a convex lens is 20 cm, what is its focal length? (2022)
A.
10 cm
B.
20 cm
C.
30 cm
D.
40 cm
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Solution
The focal length f of a lens is given by f = R/2. Therefore, f = 20 cm / 2 = 10 cm.
Correct Answer: B — 20 cm
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Q. If the radius of curvature of a convex mirror is 20 cm, what is its focal length? (2022)
A.
10 cm
B.
20 cm
C.
30 cm
D.
40 cm
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Solution
The focal length (f) of a mirror is given by f = R/2. For a convex mirror, R is positive, so f = 20 cm / 2 = 10 cm.
Correct Answer: A — 10 cm
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Q. If the resistance of a conductor is doubled while the voltage remains constant, what happens to the current? (2020)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
According to Ohm's Law, if the resistance (R) is doubled and the voltage (V) remains constant, the current (I) will be halved (I = V/R).
Correct Answer: B — It halves
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Q. If the vapor pressure of pure solvent is 100 mmHg, and the vapor pressure of the solution is 80 mmHg, what is the mole fraction of the solute? (2022)
A.
0.2
B.
0.4
C.
0.5
D.
0.8
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Solution
Using Raoult's Law: P_solution = X_solvent * P_solvent. X_solvent = P_solution / P_solvent = 80/100 = 0.8, thus X_solute = 1 - X_solvent = 0.2.
Correct Answer: B — 0.4
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Q. If two resistors of 4Ω and 12Ω are connected in series, what is the total voltage across them if the current flowing is 2A? (2020)
A.
32V
B.
24V
C.
16V
D.
8V
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Solution
Total resistance R = 4Ω + 12Ω = 16Ω. Voltage V = I * R = 2A * 16Ω = 32V.
Correct Answer: B — 24V
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Q. If two resistors of 4Ω and 6Ω are connected in parallel, what is the equivalent resistance? (2022)
A.
2.4Ω
B.
10Ω
C.
24Ω
D.
1.5Ω
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Solution
Using the formula for parallel resistors, 1/R_eq = 1/R1 + 1/R2 = 1/4 + 1/6 = 5/12, R_eq = 12/5 = 2.4Ω.
Correct Answer: A — 2.4Ω
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Q. In a chemical reaction, what does the term 'activation energy' refer to? (2023)
A.
Energy released during the reaction
B.
Energy required to initiate the reaction
C.
Energy needed to maintain the reaction
D.
Energy that is lost
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Solution
Activation energy is the minimum energy required to initiate a chemical reaction.
Correct Answer: B — Energy required to initiate the reaction
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Q. In a circuit with a 10Ω resistor and a 5V battery, what is the power consumed by the resistor? (2023)
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Solution
Power P = V^2/R = 5^2/10 = 25/10 = 2.5W.
Correct Answer: B — 2W
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Q. In a circuit with a 15V battery and a 5Ω resistor, what is the voltage drop across the resistor? (2019)
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Solution
The voltage drop across the resistor is equal to the battery voltage, which is 15V.
Correct Answer: C — 15V
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Q. In a circuit with a 15V battery and two resistors of 5Ω and 10Ω in series, what is the voltage drop across the 10Ω resistor? (2022)
A.
5V
B.
10V
C.
15V
D.
0V
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Solution
The total resistance is 15Ω. The current I = V/R = 15V/15Ω = 1A. Voltage drop across 10Ω = I * R = 1A * 10Ω = 10V.
Correct Answer: B — 10V
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Q. In a circuit with a 24V battery and a total resistance of 8Ω, what is the power consumed by the circuit? (2023)
A.
72 W
B.
48 W
C.
36 W
D.
24 W
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Solution
Power P = V^2/R = 24^2/8 = 576/8 = 72 W.
Correct Answer: B — 48 W
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Q. In a circuit with a voltage of 24V and a current of 6A, what is the resistance? (2020)
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Solution
Using Ohm's Law, R = V/I = 24V / 6A = 4Ω.
Correct Answer: D — 8Ω
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Q. In a circuit with an inductor, what happens to the current when the voltage is suddenly increased? (2020)
A.
Increases immediately
B.
Decreases immediately
C.
Increases gradually
D.
Decreases gradually
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Solution
In a circuit with an inductor, the current increases gradually due to the inductor's opposition to changes in current.
Correct Answer: C — Increases gradually
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Q. In a circuit, if the current is 5A and the resistance is 10Ω, what is the voltage? (2020)
A.
15V
B.
50V
C.
5V
D.
10V
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Solution
Using Ohm's Law, V = I * R = 5A * 10Ω = 50V.
Correct Answer: B — 50V
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Q. In a circuit, if the resistance is doubled while the voltage remains constant, what happens to the current? (2021)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
According to Ohm's law, I = V/R. If R is doubled, I will be halved.
Correct Answer: B — It halves
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Q. In a circuit, if the voltage is 24V and the current is 3A, what is the resistance? (2023)
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Solution
Using Ohm's Law, R = V / I = 24V / 3A = 8Ω.
Correct Answer: B — 6Ω
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Q. In a closed system, if a reactant is removed from the equilibrium mixture, what will happen? (2019)
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Increase in temperature
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Solution
Removing a reactant will shift the equilibrium to the left to produce more reactants, according to Le Chatelier's principle.
Correct Answer: B — Shift to the left
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Q. In a closed system, if the internal energy increases, what can be said about the work done and heat added? (2020)
A.
Work done is positive and heat added is negative
B.
Work done is negative and heat added is positive
C.
Both work done and heat added are positive
D.
Both work done and heat added are negative
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Solution
According to the first law of thermodynamics, if the internal energy increases, it implies that either work is done on the system or heat is added to the system.
Correct Answer: C — Both work done and heat added are positive
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Q. In a concave lens, the focal length is considered to be: (2023)
A.
Positive
B.
Negative
C.
Zero
D.
Infinity
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Solution
The focal length of a concave lens is considered negative as it diverges light rays.
Correct Answer: B — Negative
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Q. In a concave lens, the focal length is: (2023)
A.
Positive
B.
Negative
C.
Zero
D.
Infinite
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Solution
The focal length of a concave lens is negative, indicating that it diverges light rays.
Correct Answer: B — Negative
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