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WorksheetsRC - ELEX 1
Total questions: 50
Worksheet time: 25mins
1. Wattage rating is the maximum power that the resistor can dissipate assuming which of the following factors?
All of the choices
A standard ambient temperature
A specific life
A stated long-term drift from its no-load value.
2. For a 1/8-watt resistor, what is the maximum allowable change in resistance for a 1000-hour rated load life test?
5 %
15 %
10 %
12 %
3. An uncharged capacitor of 0.01 F is charged first by a current of 2 mA for 30 seconds and then by a current of 4 mA for 30 seconds. Find the final voltage in it.
10 V
18 V
20 V
15 V
4. To apply the superposition theorem, all components must be ______
grounded.
both nonlinear and unidirectional.
both linear and bilateral.
the active type.
5. Two coils A and B each having 1200 turns are placed near each other. When coil B is open-circuited and coil A carries a current of 5 A, the flux produced by coil A is 0.2 Wb and 30% of this flux links with all the turns of coil B. Determine the voltage induced in coil B on open-circuit when the current in the coil A is changing at the rate of 2 A/s.
28.8 V
30.4 V
26.8 V
24.9 V
6. In potentiometer terminal identification system, what color represents “always the clockwise element limit”?
Green
Yellow
Red
Blue
7. The fact that the sum of the individual branch currents equals the total current in a parallel circuit is the basis for _____.
Kirchhoff`s voltage law.
Node-voltage analysis.
Kirchhoff`s current law.
Method of mesh currents.
8. For the magnetic circuit shown below, find the current I in the coil needed to produce a flux of 0.45 mWb in the air-gap. The silicon iron magnetic circuit has a uniform cross-sectional area of 3 cm² and its magnetizing force is 3500 A/m.
0.84 A
0.81 A
0.83 A
0.82 A
9. A 400 mm length of conductor carrying a current of 25 A is situated at right-angles to a magnetic field between two poles of an electric motor. The poles have a circular cross-section. If the force exerted on the conductor is 80 N and the total flux between the pole faces is 1.27 mWb, determine the diameter of a pole face.
13.1 mm
12.4 mm
11.3 mm
14.2 mm
10. A magnetic circuit with a single air gap is shown in the figure below. The core dimensions are: Crosssectional area Ac = 1.8 × 10¯³ m², Mean core length lc = 0.6 m, Gap length g = 2.3 x 10¯³ m, N = 83 turns. Assume that the core is of infinite permeability and neglect the effects of fringing fields at the air gap and leakage flux. Calculate the reluctance of the air-gap Rg for a current i = 1.5 A.
1.17 x 10⁶ A/Wb
1.017 x 10⁶ A/Wb
1.71 x 10⁶ A/Wb
1.071 x10⁶ A/Wb
11. What class of ceramic capacitors are stable temperature-compensating capacitors that have essentially linear characteristics with properties independent of frequency over the normal range?
Class I
Class IV
Class III
Class II
12. The resistance of a wire is 'R' ohm. If it is melted and stretched to 'n' times its original length, what will be its new resistance?
n²R₁²
nR₁
nR₁²
n²R₁
13. An air capacitor has two parallel plates 10 cm² in area and 0.5 cm apart. When a dielectric slab of area 10 cm² and thickness 0.4 cm was inserted between the plates, one of the plates has to be moved by 0.4 cm to restore the capacitance. What is the dielectric constant of the slab?
5
3
1
7
14. The figure shows the motion of electrons in a wire that is near the N pole of a magnet. The wire will be pushed:
upwards
downwards
towards the magnet
away from the magnet
15. What is the relation of the electrical resistivity of ferrites to metals?
Ferrites have resistivities twice that of metal`s resistivity.
103 times that of metal`s resistivity.
Ferrites have resistivities typically 10⁶ times that of metals.
10 times that of metal`s resistivity.
16. Dissipation factor is defined as the ratio of the energy dissipated to the energy stored in the dielectric. For what dissipation factor value, where it is considered equal to the power factor of the dielectric?
Equal to 1
Less than 0.1
Equal to 10
Greater than 0.1
17. A conductor moves with a velocity of 20 m/s at an angle of 90° to a magnetic field produced between two square-faced poles of side length 2.5 cm. If the flux on the pole face is 60 mWb, find the magnitude of the induced e.m.f. in each case.
48 V
47 V
45 V
49 V
18. A magnet moves inside a coil. Consider the following factors:
I. Strength of the magnet
II. Number of turns in the coil
III. Speed at which the magnet moves
Which can affect the emf induced in the coil?
III only
I only
II only
I, and II, III
19. What is the atomic radius of copper atom?
1.41 Angstroms
1.25 Angstroms
1.17 Angstroms
1.16 Angstroms
20. Which of the following capacitor terminology refers to the ratio by which the capacitance is increased when another dielectric replaces a vacuum between two electrodes?
Relative capacitivity
All of the choices
Dielectric constant
Relative permittivity
21. The motion of ion charges in a liquid or gas is called ______.
superconductivity
the corona effect
ionization current
hole flow
22. Which of the following is NOT an industry standard in color coding potentiometer terminals for identification?
Blue
Yellow
Green
Red
23. An iron ring 30 cm mean diameter is made of square of iron of 2 cm × 2 cm cross-section and is uniformly wound with 400 turns of wire of 2 mm² cross-section. Calculate the value of the self-inductance of the coil. Assume μ_r = 800.
56.9 mH
59.6 mH
63.8 mH
68.3 mH
24. What is a small capacitance formed by twisting together two insulated wires?
Diffusion capacitance
Junction capacitance
Gimmick capacitance
Stray capacitance
25. Find the magnetic field strength and the magnetomotive force needed to produce a flux density of 0.33 T in an air-gap of length 15 mm.
3993 AT
9393 AT
3939 AT
9339 AT
1. Who invented the “electrophorus”, a device for storing an electric charge that replaced the Leyden jar?
Charles Coulomb
Joseph Priestly
Alessandro Volta
Luigi Galvani
2. What component of dielectric current is proportional to the rate of accumulation of electric charges within the dielectric?
Absorption current
Inductive current
Reactive current
Apparent current
3. An electron traveling north enters a region where the electric field is uniform and points west. The electron:
veers east
veers west
speeds up
slows down
4. When multiplying complex numbers in polar form, _____.
multiply the magnitudes and add the phase angles
multiply the magnitudes and subtract the phase angles
multiply the angles and add the magnitudes
multiply both the magnitude and phase angles
5. What element property represents the relative tendency of an atom to attract shared electron pairs?
Electronegativity
Protopositivity
Work function
First ionization potential
6. A rectangular loop of wire has area A. It is placed perpendicular to a uniform magnetic field B and then spun around one of its sides at frequency f. The maximum induced emf is:
BAf
2BAf
π BAf
2π BAf
7. If the magnetic flux through a certain region is changing with time:
an emf must exist around the boundary
an electric field must exist at the boundary
a current must flow around boundary
energy must be dissipated as heat
8. What capacitor terminology includes power factor, loss factor and dielectric loss?
Quality factor
Cosine of loss angle
Tangent of loss angle
Dissipation factor
9. Which one of the following statements is incorrect at 0°K?
Insulators have a wide energy gap.
The valence and conduction bands of an intrinsic semiconductor overlap.
Metals have empty states in the valence band.
Insulators have a filled valence band
10. What static electricity is produced by rubbing silk on a glass rod?
Resinous static electricity
Negative electricity
Positive electricity
Vitreous static electricity
11. Determine the transition capacitance of a diffused junction varicap diode at a reverse potential of 4.2 V if C(0) = 80 pF and V_T = 0.7V.
41.82 pF
5.28 pF
3.48 pF
3.38 pF
12. Which of the following statements is correct?
Electrons are the majority carriers in boron-doped silicon.
Silicon has a greater intrinsic conductivity than does germanium
Semiconductivity increases linearly with temperature.
Semiconductivity is proportional to the product of the number and the mobility of carriers.
13. The electric field due to a uniform distribution of charge on a spherical shell is zero:
only at the center of the shell
everywhere
nowhere
only inside the shell
14. In intrinsic semiconductor, the formation of holes and free electrons increases with temperature and is known as _______.
natural carrier generation
thermal carrier generation
intrinsic carrier generation
normal carrier generation
15. For the circuit shown below, determine v_a.
7.68 V
6.87 V
8.67 V
8.76 V
16. What will be the equivalent resistance of the circuit shown in figure between two points A and D?
40 Ω
10 Ω
20 Ω
30 Ω
17. For the circuit shown, find i₁.
2.09 A
2.90 A
1.9 A
1.09 A
18. A charge Q is divided into two parts of q and Q – q. If the coulomb repulsion between them when they are separated is to be maximum, what should be the ratio of Q/q?
1:2
2:1
1:1.5
1.5:1
19. An electric field strength created by charge Q is measured to be 40 N/C at a distance of 0.2 m from the center of the charge. What is the new field strength when the distance from the center of Q is changed to 0.4 m away with twice the charge of Q?
20 N/C
40 N/C
30 N/C
50 N/C
20. Determine the diode current at 20°C for a silicon diode with I_s = 0.1 µA at a reverse-bias potential of -10 V
0.01 µA
0.10 µA
0.10 nA
0.01 nA
21. Which of the following does not contribute to the permanence of a magnet?
Cold working
Minor phases
Grain growth
Crystal anisotropy
22. Given P_max = 14 mW for each diode, determine the maximum current rating of each diode (using the approximate equivalent model).
15 mA
5 mA
20 mA
10 mA
23. What static electricity is produced by rubbing fur on a rubber, amber or plastic rod?
Negative electricity
Resinous static electricity
Vitreous static electricity
Positive electricity
24. Silicon becomes an extrinsic semiconductor with electrons as the majority carrier when doped with ________.
antimony
germanium
boron
aluminum
25. In an ac circuit with only parallel inductors.
V_A lags I_T by 90°
None of the choices
I_T lags V_A by 90°
V_A and I_T are in phase
