NUMERICALS
Electricity & its effects
21. An electric lamp, whose resistance is 20 Ω, and a conductor of 4 Ω resistance are connected to a 6 V battery . Calculate
(a) The total resistance of the circuit,
(b) The current through the circuit, and
(c) The potential difference across the electric lamp and conductor.
22. a) Draw a schematic diagram of a circuit consisting of a battery of three cells of 2 V each, a 5 Ω resistor, an 8 Ω resistor, and a 12 Ω resistor, and a plug key, all connected in series.
b) Redraw the circuit of above, putting in an ammeter to measure the current through the resistors and a voltmeter to measure the potential difference across the 12 Ω resistor. What would be the readings in the ammeter and the voltmeter.
23. In the given Figure R1 = 10 Ω, R2 = 40 Ω, R3 = 30 Ω, R4 = 20 Ω, R5 = 60 Ω, and a 12 V battery is connected to the arrangement. Calculate
(a) The total resistance in the circuit.
(b) The total current flowing in the circuit.
24. Judge the equivalent resistance when the following are connected in parallel – (a) 1 Ω and 106 Ω (b) 1 Ω and 103 Ω, and 106 Ω.
25. What is (a) the highest, (b) the lowest total resistance that can be secured by combinations of four coils of resistance 4 Ω, 8 Ω, 12 Ω, 24 Ω?
26. In the circuit diagram below the current through 5 Ω resistance is 1A. Find
(i) Current through the other two resistor?
(ii) What is the potential difference across AB and across AC?
(iii) What is the total resistance. [2003]
27. A piece of wire having a resistance R is cut into four equal parts.
(i) How will the resistance of each part of the wire will compare with the original resistance?
(ii) If the four parts of the wire are placed in parallel, how will the resistance of the combination compare with the resistance of the original wire?
28. When two resistances R1 & R2 are connected in parallel, the net resistance is 3Ω. When connected in series, its value is 16Ω. Calculate the value of R1 & R2 . [2002]
