RC - ELEX 1

1. 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. 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