- A2 I
- ✓4 I
- C5 I
- DI
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Work function of a metal is 2.51 eV. Its threshold frequency is
|
(a) 5.9 |
(b) 6.5 |
|
(c) 9.4 |
(d) 6.08 |
The heating coils rating at 220 volt and producing 50 cal/sec heat are available with the resistances 55Ω,110 Ω, 220 Ω and 440 Ω. The heater of maximum power will be of
|
(a) 440 Ω |
(b) 220 Ω |
(c) 110 Ω |
(d) 55 Ω |
Two heater wires of equal length are first connected in series and then in parallel. The ratio of heat produced in the two cases is
|
(a) 2 : 1 |
(b) 1 : 2 |
(c) 4 : 1 |
(d) 1 : 4 |
A step-down transformer is connected to 2400 volts line and 80 amperes of current is found to flow in output load. The ratio of the turns in primary and secondary coil is 20 : 1. If transformer efficiency is 100%, then the current flowing in primary coil will be
|
(a) 1600 A |
(b) 20 A |
(c) 4 A |
(d) 1.5 A |