Physics Exam

1. The magnetic field created by a long straight current carrying wire

A. is inversely proportional to the current in the wire.
B. is directly proportional to the distance from the wire.
C. forms circular pattern around the wire.
D. is directed in the same direction as the current.

2. We usually use plastic materials to cover metallic wires that carry electricity to protect living things from danger. Which of the following statement correctly describes the nature of the plastic to use for this purpose?

A. Since it has no free electrons, it directs the electrons in the wire to flow in the same direction.
B. Since it has free electrons, it facilitates the easy flow of electric current in the metallic wires.
C. Since every electron in plastic is tightly bound to the parent atom, it becomes poor conductor.
D. Since every electron in plastic is slightly bound to the parent atom, it becomes poor conductor.

3. What will happen on a pure semiconductor when it is doped by group III element?

A. It becomes P-type semiconductor.
B. It becomes N-type semiconductor.
C. It gets extra free electrons.
D. It becomes intrinsic semiconductor.

4. Which one of the following statements is correct about the current-voltage (I-V) characteristics of a typical semiconductor diode?

A. The current due to the majority charge carriers is represented in the reverse bias region of the I-V curve
B. The current due to the minority charge carriers is represented in the forward bias region of the I-V curve.
C. The region of the I-V curve that increases very rapidly after the bias voltage exceeds the breakdown voltage is in the forward bias region.
D. The region of the I-V curve that rises very rapidly after the voltage exceeds the cut-in voltage is the forward bias region.

5. Consider a circuit containing diode and load resistor (RL) are connected to an AC voltage source as shown in the figure below.

If initially, polarity of 'a' is positive while 'b' is negative,

A. During the second half-cycle, the diode is reverse biased and no current flow in the load resistor.
B. During the first half-cycle, the diode is forward biased and voltage is developed across the load resistor.
C. During the first half-cycle, the diode is reverse biased and voltage is developed across the load resistor.
D. During the second half-cycle, the diode is forward biased and current flows in the load resistor.

6. A circular coil is located in a uniform magnetic field of magnitude 0.50 T directed perpendicular to the plane of the coil. If the area of the coil changes with uniform rate, in such a way that it increases by 4.0 × 10⁻³ m² in 2 s, what is the magnitude of the induced electromotive force (emf) in the coil?

A. 4.0 × 10⁻³ V
B. 1.0 × 10⁻³ V
C. 1.0 × 10³ V
D. 2.5 × 10² V

7. If two vectors $\vec{a}$ and $\vec{b}$ , 6 with respective magnitudes of a and b, form an angle a between them when they are connected tail to tail, then the expression ab cos a defines the value of

A. scalar product of

\vec{a}

and

\vec{b}

.
B. resultant of

\vec{a}

and

\vec{b}

.
C. projection of

\vec{a}

and

\vec{b}

.
D. Vector product of

\vec{a}

and

\vec{b}

.

8. Which one of the following statements is correct about real and virtual images?

A. Real images can be magnified but virtual images cannot.
B. Virtual images can be magnified but real images cannot.
C. Virtual images can be displayed on a screen unlike the real ones.
D. Real images can be displayed on a screen unlike the virtual ones.

9. An object moving in one dimension with constant acceleration α travels through a displacement s in a time interval t. If its velocity at the initial time t = 0 is v_i and its velocity at a later time t is v_f, which of the following is a correct relation between the given quantities?

A. s = ((v_f - v_i)/2)t
B. s = (v_f² - v_i²)/α
C. s = v_it + (1/2)αt²
D. s = v_ft - (1/2)αt²

10. If the critical angle for an optically denser medium to air boundary is 53°, what will be the refractive index of the medium? (Assume the index of refraction of air is 1.00, sin53° = cos37° = 0.8, cos53° = sin37° = 0.6)

A. 1.25
B. 1.00
C. 1.33
D. 1.67

11. Given the displacement vector $\vec{A}$ = (3î - 4j) m, what is the unit vector in the direction of Ᾱ?

A. 0.6î +0.8 ĵ
B. 0.8 î-0.6 ĵ
C. 0.6 î - 0.8ĵ
D. -0.6î +0.8 ĵ

12. Suppose that you are given two forces with F₁ = 75 N in the direction of 53° wests of north and F₂ = 100 N in the direction of 37° east of north. If you add the two forces using analytical and graphical methods and represent using graphical scale of 1 cm for 10 N force, what are the possible length and direction of the arrow line for the resultant vector?

A. 1.73 cm to 45° North of East
B. 1.25 cm to the North
C. 17.3 cm to 45° North of East
D. 12.5 cm to the North

13. The amount of heat energy required to raise the temperature of a given substance by 1°C is

A. specific heat capacity.
B. heat capacity.
C. quantity of heat.
D. latent heat.

14. Which one of the following statements is correct about the properties of waves?

A. Diffraction of a wave through a narrow gap is more observable than through a wider gap.
B. When two waves interfere destructively, the amplitude of the resultant wave is greater than the amplitude of each wave.
C. When a wave is refracted, its speed and wavelength remain the same.
D. When a wave is reflected, its speed and wavelength are changed.

15. A square metal plate of coefficient of linear expansion α, has a surface area A₀ at a temperature T₀. If the temperature is raised by an amount ▲T, then the plate surface area is changed to A which is expressed as

A. A = 2A₀ (1+ α▲T).
B. A = A₀ (1+ 2α▲T).
C. A = A₀ (1+ 3α▲T).
D. A = A₀ (1+ α▲T).

Physics Exam: Part 1

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