DC Circuit MCQ Job Interview Exam Higher Study Admission Questions Answers part3
1. Identical wires of nichrome and copper are connected in series in a circuit. This results in greater heat in nichrome.
2. Two resistance are in parallel and give equivalent resistance of 6/5 Ω. One of the resistances is broken and the effective resistance is 2 Ω. The resistance of the broken resistor is 3 Ω.
3. Two identical cells connected in series send 10 A through 5 Ω resistor. When they are connected in parallel, they send 8 A through the same resistor. The terminal resistance of each cell is 2.5 Ω.
Let E and r be the e.m.f and internal resistance of each cell.
For series grouping, 2E =(5+2r)*10…..(1)
For parallel grouping, E=(5+r/2)*8 …..(2)
Solving eq (1) & (2), r=2.5Ω
4. Two batteries of different e.m.fs and same internal resistances are connected in series with an external resistance and current is 3 A. When polarity of one is reversed, the current is 1 A. The ratio of e.m.f s is 2.
5. n similar resistors each of resistance r when connected in parallel have the total resistance R,
When these resistances are connected in series, the total resistance is n^2R.
6. Kirchhoff’s current law at a junction deals with conservation of charge.
7. Kirchhoff’s voltage law deals with conservation of energy.
8. A cell supplies a current of 0.9 A through 2 Ω external resistance and 0.3 A through 7 Ω external resistance. The internal resistance of the cell is 0.5 Ω.
Let E and r be the e.m.f,
For the first case 0.9= E/2+r ,
For the second case 0.3= E/7+r ,
Solving these two equation r= 0.5 Ω
9. A 50 V battery is connected across 10 Ω resistor. The current is 4.5 A. The internal resistance of the battery is 1.1 Ω.
10. An ordinary dry cell can deliver a current of about 1/8 A or 0.125 A.
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