1. | \(20~\mathrm{V}\) and \(2.0~\mathrm{mA}\) |
2. | \(10~\mathrm{V}\) and \(0.5~\mathrm{mA}\) |
3. | zero and therefore no current |
4. | \(20~\mathrm{V}\) and \(0.5~\mathrm{mA}\) |
A \(220\) V input is supplied to a transformer. The output circuit draws a current of \(2.0\) A at \(440\) V. If the efficiency of the transformer is \(80\)%, the current drawn by the primary windings of the transformer is:
1. \(3.6\) A
2. \(2.8\) A
3. \(2.5\) A
4. \(5.0\) A
A transformer is used to light a \(100~\text{W}\) and \(110~\text{V}\) lamp from a \(220~\text{V}\) main. If the main current is \(0.5~\text{A}\), the efficiency of the transformer is approximately:
1. \(30\%\)
2. \(50\%\)
3. \(90\%\)
4. \(10\%\)
The core of a transformer is laminated so that:
1. | energy losses due to eddy currents may be minimized |
2. | the weight of the transformer may be reduced |
3. | rusting of the core may be prevented |
4. | the ratio of voltage in primary and secondary may be increased |