Electrical Engineering Mcqs

Magnetic flux has the unit of

A. Newton
B. Ampere-turn
C. Weber
D. Tesla

The unit of magnetic flux is called Weber in honor of famous scientist Wilhelm Eduard Weber (1804 – 1891). Magnetic flux has also another unit named Maxwell. 1 Maxwell = 10-8 Weber.

 If P is the power of a star connected system then what will be power of an equivalent delta connected system?A. P
B. 3P
C. P/3
D. None of the above

Assume 3 numbers of pure resistive loads each of value R.
When these loads are connected in delta the power in each resistor is V^2/R and the total power is 3×V^2/R.
When these loads are connected in star the voltage applied across each = V/(sqrt of 3). Power in each load becomes = V^2/(3×R) . and the total load is =(3×V^2)/(3×R)=V^2/R. You can see this is 3 times less than the total power when the loads are connected in delta.
One important point is that the loads should withstand higher voltage (line voltage) and higher current when connected in delta than when they are connected in star
so power in delta is 3 time power correct answer is 3P

 

Which of the followings is/are active element?

A. Voltage source
B. Current source
C. Both
D. None of these.

Active elements are capable of delivering energy independently for long time or ideally infinite time. Both voltage and current source are active element and they can change energy level of a circuit.