Current Electricity-05-C.B.S.E. LEVEL - I

C.B.S.E. LEVEL - I (REVIEW YOUR CONCEPTS) 1. A battery of emf 10V and internal resistance 3 is connected to a resistor. If the current in the circuit is 0.5A, what is the resistance of the resistor? What is the terminal voltage of the battery when the circuit is closed? 2. (a) Three resistors 1, 2 combination? and 3 are combined in series. What is the total resistance of the (b) If the combination is connected to a battery of emf 12V and negligible internal resistance, obtain the potential drop across each resistor. 3. Find the potential differnce across the capacitor in following figure 3 15V 4. The storage battery of a car has an emf of 12V. If the internal resistance of the battery is 0.4 , what is the maximum current that can be drawn from the battery? 1. ) In a metre bridge, (Figure) the balance point is found to be at 39.5 cm from the end A, when the resistor Y is of 12.5  . Determine the resistance of X. Why are the connections between resistors in a Wheatstone or metre bride made of thick copper strips? (b) Determine the balance point of the bridge above if X and Y are interchanged. (c) What happens if the galvanometer and cell are interchanged at the balance point of the bridge? Would the galvanometer show any current? (a) (c) 2. alvanometer coil has a resistance of 12 and the metre shows full scale deflection for a current of 3 mA. How will you convert the meter into a voltmeter of range 0 to 18V ? 3. a potentiometer arrangement, a cell of emf 1.25 V gives a balance point at 35.0 cm length of the wire. If the cell is replaced by another cell and the balance point shifts to 63.0 cm, What is the emf of the second cell? 4. e number density of conduction electrons in a copper conductor is 8.5 1028 m3 . How long does an electron take to drift from one end of a wire 3.0 m long to its other end? The area of cross-section of the wire is 2.0 106 m 2 and it is carrying a current of 3.0 A. 5. the circuit shown what are the potential at B, C and D ? A 1 12 V B 0  6 V C  D 6. Six lead-acid type of secondary cells each of emf 2.0V and internal resistance 0.015  are joined in series to provide a supply to a resistance of 8.5  . What are the current drawn from the supply and its terminal voltage? (b) A secondary cell after long use has an emf of 1.9V and a large internal resistance of 380  . What maximum current can be drawn from the cell? 7. Given n resistors each of resistance R, how will you combine them to get the (i) maximum (ii) Minimum effective resistance? What is the ratio of the maximum to minimum resistance? (b) en the resistances of 1, 2, 3 , how will be combine them to get an equivalent resistance of (i) (11/3)  (ii) (11/5)  , (iii) 6 , (iv) (6/11)  ? (c) ermine the equivalent resistance of networks shown in figure. R (a) (b) 8. ermine the current drawn from a 12V supply with internal resistance 0.5 by the infinite net- work shown in figure. Each resistor has 1 resistance. 1 1 1 1 1 1 1 1 (12V, 0.5 1 1 1 1 1 9. A battery of emf 9V and negligible internal resistance is connected to a 3k resistor. The potential drop across a part of the resistor (between points A and B in figure) is measured by (i) a 20k voltmeter, (ii) a 1k voltmeter. In (iii) both the voltmeters are connected across AB. In which case would you get the (1) highest, (2) lowest reading? (b) our answers to this problem alter if the potential drop across the entire resistor is mea- sured? What if the battery has non-negligible internal resistance? 20k  (a) (b) (c) 10. lly charged capacitor of capacitance C is connected to two voltmeter A and B. A is ideal while B has a resistance R. If the switch S is closed at t = 0. What time, reading of A and B will be equal ? S 11. current I through a rod of a certain metallic oxide is given by I = 0.5V2 , where V is the potential difference across it. The rod is connected in series with a resistance to a 6V battery of negligible internal resistance. What value should the series resistance have so that : (a) The current in the circuit is 1/2 Amp (b) The power dissipated in the rod is twice that dissipated in the resistance.

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