Sinusoidal AC

Q.

An alternating voltage is represented as $E=20\sin 300t$. The average value of voltage over one cycle will be

1. $zero$

2. $10volt$

3. $20\sqrt{2}volt$

4. $(20/\sqrt{2})volt$

Q. The voltage of domestic ac is 220 volt. What does this represent

1. Mean voltage
2. Peak voltage
3. Root mean voltage
4. Root mean square voltage

Q. The peak value of an alternating e.m.f. E is given by $E=E_{0}cos\omega t$ is 10 volts and its frequency is 50 Hz. At time $t=\frac{1}{600}sec,$ the instantaneous e.m.f. is

1. $10V$
2. $5\sqrt{3}V$
3. $5V$
4. $1V$

Q. The voltage of an ac supply varies with time (t) as V = $120sin100\pi tcos100\pi t$ The maximum voltage and frequency respectively are

1. 120 volts, 100 Hz
2. $\frac{120}{\sqrt{2}}$ volts , 100 Hz
3. 60 volts, 200 Hz
4. 60 volts, 100 Hz

Q. Match the following
$\begin{array}{cc}Currents& r.m.svalues\\ \left(1\right)x_{0}sin\omega t& \left(i\right)x_0\\ \left(2\right)x_{0}sin\omega tcos\omega t& \left(ii\right)\frac{x_0}{\sqrt{2}}\\ \left(3\right)x_{0}sin\omega t+x_{0}cos\omega t& \left(iii\right)\frac{x_0}{\left(2\sqrt{2}\right)}\end{array}$

1. 1. (i), 2. (ii), 3. (iii)
2. 1. (ii), 2. (iii), 3. (i)
3. 1. (i), 2. (iii), 3. (ii)
4. None of these

Q. The voltage of domestic ac is 220 volt. What does this represent

1. Mean voltage
2. Peak voltage
3. Root mean voltage
4. Root mean square voltage

Q. An electric lamp is connected to 220 V, 50 Hz supply. Then the peak value of voltage is

1. 210 V
2. 211 V
3. 311 V
4. 320 V

Q. A resistance of 20 ohms is connected to a source of an alternating potential $V=220sin\left(100\pi t\right)$. The time taken by the current to change from its peak value to r.m.s value is

1. $0.2sec$
2. $0.25sec$
3. $25\times {10}^{-3}sec$
4. $2.5\times {10}^{-3}sec$

Q. An alternating voltage is represented as E=20 sin 300 t. The average value of voltage over one cycle will be

1. $Zero$
2. $10volt$
3. $20\sqrt{2}volt$
4. $\frac{20}{\sqrt{2}}volt$

Q. An electric lamp is connected to 220 V, 50 Hz supply. Then the peak value of voltage is

1. 210 V
2. 211 V
3. 311 V
4. 320 V

Q. Voltage of an AC source is given by V= 200sin$\left(100\pi t\right).cos\left(100\pi t\right)$ where t is in seconds and V is in volts. Then the peak voltage is
volts.

1. 50
2. 100
3. 200
4. 400

Q. An ac voltage is represented by $E=220\sqrt{2}cos\left(50\pi \right)t$. The current becomes zero times in 1 sec.

1. 25
2. 50
3. 75
4. 100

Q. The peak value of an alternating emf is given by $E=E_{0}cos\left(wt\right)$ is 10 volt and its frequency is 50 Hz. At a time $t=\left(\frac{1}{600}\right)$ second, the instantaneous value of the emf is:

1. 1V
2. 5V
3. $5\sqrt{3}V$
4. 10V

Q. The voltage of an ac source varies with time according to the equation $V=100sin100\pi tcos100\pi t$ where t is in seconds and V is in volts. Then

1. The peak voltage of the source is 100 volts
2. The peak voltage of the source is 50 volts
3. The peak voltage of the source is $\frac{100}{\sqrt{2}}$ volts
4. The frequency of the source is 50 Hz

Q.

An ac voltage is represented by $E=220\sqrt{2}cos\left(50\pi \right)t$ How many times will the current becomes zero in 1 s?

1. 50 times

2. 100 times

3. 30 times

4. 25 times

Q. A resistance of 20 ohms is connected to a source of an alternating potential $V=220sin\left(100\pi t\right)$. The time taken by the current to change from its peak value to r.m.s value is

1. $0.2sec$
2. $0.25sec$
3. $25\times {10}^{-3}sec$
4. $2.5\times {10}^{-3}sec$

Q.

An ac voltage is represented by $E=220\sqrt{2}cos\left(50\pi \right)t$ How many times will the current becomes zero in 1 s?

1. 50 times

2. 100 times

3. 30 times

4. 25 times