681. Electromagnetic waves transport___________________?
A. Energy
B. Momentum
C. Mass
D. Heat
682. Electromagnetic waves emitted from antenna are________________?
A. Stationary
B. Longitudinal
C. Transverse
D. All the above
683. A capacitor of capacitance 30µF is charged by a constant current of 10mA. If initially, the capacitor was uncharged what is the time taken for the potential difference across the capacitor to reach 300V ?
A. 0.9sec
B. 15 sec
C. 1.5x105sec
D. 0.9x102sec
684. To find the r.m.s value of an alternating current mathematically we need to have ________________?
A. Mean value of I2
B. Square root of mean value of I2
C. Square root of I2
D. Square of 1/2
685. An alternating current is represented by the equation I = I∫sinπt which of the following equation represents an alternating current of frequency and amplitude twice that of the above current ?
A. I = 2I∫Sin(πt/2)
B. I = 2I∫Sin(2πt)
C. I = 2ISinπt
D. I = I∫sin(2πt)
686. pure resistor circuit the voltage and current are_______________?
A. Lagging each other
B. They are at 90? phase difference
C. They have zero phase difference
D. No phase difference
687. When A.C current passes through a capacitor then the current relationship will be_______________?
A. The current lead voltage by phase angle is 90 degrees
B. The voltage leads current by phase angle is 90 degrees
C. The current lead voltage by phase angle is 45 degrees
D. The voltage leads current by phase angle is 45 degrees
688. In the capacitive circuit the current___________________?
A. Lags behind voltage by π/2
B. Is in phase with voltage
C. Opposite in phase of voltage by π
D. Leads forward the voltage by π/2
689. A 100µF capacitor with a 12V source in series having frequency 50Hz will offer a capacitive reactance of about______________?
A. 32Ω
B. 62Ω
C. 50Ω
D. 100Ω
690. If a glass plate is inserted in between the plate of a capacitor in series with a lighted bulb the brightness of the bulb________________?
A. Remains same
B. Brightness increases
C. Brightness decreases
D. No light