POST UTME REDEEMERS UNIVERSITY 2020 Physics | Objective

Practice these randomly selected questions to test your readiness.

Question 1
A coil of wire with $N$ turns and radius $r$ carries a current $I$. The coil is placed in a uniform magnetic field $B$ directed perp\endicular to the plane of the coil. Find the magnitude of the torque τ exerted on the coil.
A. NIBr^2
B. NIBr
C. NIB
D. NIBr^3
Question 2
A block of mass $m$ is susp\ended from a spring with spring cons\tant $k$. If the block is displaced by a dis\tance $x$ from its equilibrium position and released from rest, its subsequent motion is described by the equation $x(t) = A \cos\( omega t + phi \)$, where $A$ is the amplitude of the motion, $omega$ is the angular frequency, and $phi$ is the phase angle. If the block is observed to have a maximum speed of $v_{max} = 2\sqrt{2} , \text{m/s}$, what is the value of the spring cons\tant $k$?
A. 10 N/m
B. 20 N/m
C. 30 N/m
D. 40 N/m
Question 3
A parallel plate capacitor has plates of area 0.04 m^2 and separation 0.02 m. If the dielectric cons\tant of the material between the plates is 3, calculate the capaci\tance.
A. 1.6 x 10^-10 F
B. 3.2 x 10^-10 F
C. 4.8 x 10^-10 F
D. 6.4 x 10^-10 F
Question 4
A 100 Ω resistor is connected in series with a 50 Ω resistor and a 200 Ω resistor. What is the total resis\tance of the circuit?
A. 100 Ω
B. 150 Ω
C. 200 Ω
D. 250 Ω
Question 5
A particle of mass $m$ and charge $q$ is moving in a circular path of radius $r$ in a uniform magnetic field of strength $B$. If the particle's speed is $v$, what is the magnitude of the magnetic force acting on it?
A. \frac{mv^2}{r}
B. \frac{mv^2}{2r}
C. \frac{mv^2}{3r}
D. \frac{mv^2}{4r}
Question 6
A circuit consists of a 12 V battery, a 4 Ω resistor, and a 6 Ω resistor connected in parallel. If the current through the 4 Ω resistor is 2 A, calculate the current through the 6 Ω resistor.
A. 1 A
B. 2 A
C. 3 A
D. 4 A
Question 7
A parallel-plate capacitor has plates of area $A$ and separation $d$. The capacitor is charged to a potential difference $V$. What is the energy stored in the capacitor?
A. \frac{1}{2}CV^2
B. \frac{1}{2}AV^2
C. \frac{1}{2}dV^2
D. \frac{1}{2}AVd
Question 8
A photon of energy $E$ is incident on a metal surface. If the work function of the metal is $\phi$, what is the maximum kinetic energy of the ejected electron?
A. E - \phi
B. E + \phi
C. \phi - E
D. \phi + E
Question 9
A light source is placed 2 meters away from a convex lens of focal length 0.5 meters. What is the image dis\tance?
A. 1 meter
B. 2 meters
C. 3 meters
D. 4 meters
Question 10
A capacitor consists of two parallel plates, each of area $A$ and separation $d$. The plates are charged to a potential difference $V$ and then connected to a battery of emf $E$. If the battery is removed and the capacitor is left to discharge, what is the time cons\tant of the discharge?
A. RC
B. RC/2
C. RC/3
D. RC/4
Question 11
A charged particle is placed in a uniform electric field. If the particle's charge is 2 μC and the electric field strength is 100 N/C, what is the force exerted on the particle?
A. 0.2 N
B. 0.4 N
C. 0.6 N
D. 0.8 N
Question 12
A heat engine operates between two temperatures $T_1$ and $T_2$, with $T_1 > T_2$. The engine has an efficiency ε of 30%. Find the temperature $T_2$ in Kelvin, given that $T_1 = 500 K$.
A. 300 K
B. 400 K
C. 500 K
D. 600 K
Question 13
A particle of mass 0.2 kg is moving in a circular path with a radius of 0.5 m. If the particle has a speed of 2 m/s, calculate the centripetal acceleration.
A. 0.1 m/s^2
B. 0.2 m/s^2
C. 0.3 m/s^2
D. 0.4 m/s^2
Question 14
A 10 Ω resistor is connected in parallel with a 20 Ω resistor. What is the equivalent resis\tance of the circuit?
A. 6.67 Ω
B. 8.33 Ω
C. 10 Ω
D. 12.5 Ω
Question 15
A 100 Ω resistor is connected in parallel with a 200 Ω resistor. What is the equivalent resis\tance of the circuit?
A. 50 Ω
B. 66.67 Ω
C. 100 Ω
D. 200 Ω

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