Lecture 10

What is direct current (DC)?

• A current that flows in one direction

• A current that flows in multiple directions

• A type of current used in AC systems

• A type of current that changes direction periodically

What is the formula for Ohm's law?

• V = I x R

• P = V x I

• E = P x Time

• I = V/R

What does the power factor in AC circuits depend on?

• The type of electrical load connected

• The voltage supplied

• The current flowing

• The frequency of the supply

What is the voltage between any two actives in a three-phase system?

• 1.73 times the single phase voltage

• 230 V

• 400 V

• Zero

Fill in the blank: The electrical resistance of the cable is analogous to the ______ of the water flowing in the pipe.

What are the advantages of 3 Phase Circuits?

• Electric power is generated and distributed in the three-phase system only.

• The instantaneous power in a three-phase system is always constant.

• The amount of wire required for a 3-phase system is lesser than that required for an equivalent 1-phase system.

• For similar power, the three-phase system is more economical than the single-phase.

What is the root mean square (rms) value of an alternating supply?

• It is the equivalent value that gives the same power as a constant DC supply of the same voltage.

• It is the maximum voltage of the AC supply.

• It is the average voltage of the AC supply.

• It is the minimum voltage of the AC supply.

What is the basic operating principle of an AC generator?

• It rotates a magnetic field around a set of stationary wire coils.

• It converts mechanical energy into electrical energy.

• It uses a battery to generate electricity.

• It relies on solar energy to produce power.

What is the function of a transformer?

• To change the voltage of AC electricity.

• To store electrical energy.

• To convert AC to DC.

• To generate electricity.

What happens to the power lost in transmission lines?

• It must be reduced to a practical minimum.

• It is stored for later use.

• It is converted to heat and used.

• It is transferred to the consumer.