Engineering Board Exam Reviewer · Alternating Current and Voltage · hard
Two currents i1=10 t A and i2=10 ( t+120°) A flow into a junction and add. What is the peak value of the total current?
- 10 A
- 20 A
- 17.3 A
- 14.1 A
Answer
A. 10 A
Solution
As phasors: 10 0°+10 120°=(10-5)+j8.66=5+j8.66=10 60°. The peak value is 10 A (two equal phasors 120° apart add up to the same magnitude).
More Alternating Current and Voltage questions
- How long does it take a 400 Hz sine voltage, starting at zero, to reach 70.7% of its peak value for the first time?
- A sinusoidal voltage has an rms value of 120 V. At what angle in the first quadrant of the cycle does its instantaneous value equal 100 V?
- The rectangular pulse train shown has a period of 10 ms and is at 20 V for the first 4 ms of each period and zero for the rest. Find its…
- The voltage shown is a sine wave riding on a dc level (it swings between -10 V and +30 V). Find its rms value.
- Two series-connected sources produce v1=30 t V and v2=40 ( t+90°) V. What is the peak value of the total voltage?
- A sinusoidal voltage with a peak value of 100 V is applied across a 50, resistor. What average power does the resistor dissipate?
- How long does a 60 Hz sine wave take to go from zero to 45° of its cycle?
- Given v=100 ( t+20°) V and i=8 ( t-40°) A, which statement is correct?
- A voltage is given by v=311 (377t) V. What is its frequency?
- The waveform shown is a full-wave rectified sine voltage. Find its average (dc) value.