EE Pre Test

The resistance of a winding wire made up of copper is 25 ohm at 30 deg C. What is its resistance when it operates at a temperature pf 75 deg C? Assume temperature coefficient at 20 deg C = 0.004.

• 29.33 ohm

• 28.36 ohm

• 30.67 ohm

• 31.69 ohm

A 100 watt bulb takes 0.833 amperes and a 200 watt bulb takes 1.666 amperes from a 120 volt power line. If the two bulbs were connected across a 240 volt power line, what current in amperes will flow through the bulbs?

• 2.22

• 4.44

• 3.33

• 1.11

Which of the following statements is incorrect?

• Voltages in a circuit are usually measured with respect to the ground or earth connection.

• If a body develops an excess of electrons it will have an overall positive charge.

• Conventional current is in the opposite direction to a flow of electrons.

• An e.m.f. represents the energy introduced into a circuit by a battery or generator.

The drift velocity of an electron is

• Very small as compared to speed of the light

• Equal to speed of the light

• Almost equal to the speed of the light

• Greater than the speed of the light

Which Three resistors, each of R ohms, are connected to form a triangle? The resistance between any two terminals will be:

• 2/3 R

• 3/2R

• 3R

• R

A battery is connected to a resistance causing a current of 0.5A in the circuit. The current drops to 0.4 when an additional resistance of 5 is connected in series. The current will drop to 0.2A when the resistance is further increased by

• 10 ohm

• 15ohm

• 25ohm

• 5 ohm

The plates of a parallel-plate capacitor are 5mm apart and 2 𝑚2 in area. A potential difference of 10,000V is applied across the capacitor. Compute the charge on each plate.

• 26.3 µC

• 63.9 µC

• 12.8 µC

• 35.4 µC

Compute the wye-equivalent of delta connected capacitor 3µF, 4µF, and 5µF.

• 21.75µF, 9.4µF, and 15.67µF

• 11.75µF, 9.4µF, and 15.67µF

• 11.75µF, 9.4µF, and 16.67µF

• 11.75µF, 8.4µF, and 16.67µF

Electric pressure is also called

• Resistance

• Power

• Voltage

• Energy

Four wires of same material, the same cross-sectional area and the same length when connected in parallel give a resistance of 0.25 ohm. If the same four wires are connected is series the effective resistance will be

• 1 ohm

• 2 ohm

• 3 ohm

• 4 ohm