Tiêu đề 03. CURRENT ELECTRICITY.pdf ✅

28. Assertion : A potentiometer draws no current while measur‐ ing emf of a cell. Reason : Voltmeter is much better than a potentiometer for measuring emf of cell. (1) Both Assertion and Reason are cor- rect and Reason is the correct explana- tion of the Assertion. (2) Both Assertion and Reason are cor- rect but Reason is not the correct explana- tion of the Assertion. (3) Assertion is cor- rect but Reason is incorrect. (4) Assertion is incor- rect but reason is correct. 29. Two wires and of equal lengths are con‐ nected in left and right gap of a meter bridge, null point is obtained at 40 from left end. Diameter of the wire and are in that ratio 3 : 1. The ratio of specific resistance of to that of is (1) (2) (3) (4) 30. In the circuit shown, the value of in ampere is (1) (2) (3) (4) 31. The reading of the ammeter as per figure shown in below (1) (2) (3) (4) 32. In order to obtain time constant of in an circuit containing a resistance of , the capacity of the condenser should be (1) (2) (3) (4) 33. Four resistances of and respectively taken in order are used to form a Wheatstone's bridge. battery is con‐ nected to the ends of a resistance, the cur‐ rent through it will be (1) (2) (3) (4) 34. Two bulbs rated 25 -220 and 100 -220 are connected in series to a 440 supply. Then, (1) 100 bulb fuses (2) 25 bulb fuses (3) both the bulbs fuse (4) neither of the bulb fuses 35. In a closed circuit, the current (in ampere) at an instant of time (in second) is given by . The number of electrons flowing in 50 through the cross-section of the conduc‐ tor is. (1) (2) (3) (4) 36. Two resistances are given as and . The percentage error in the measurement of equivalent resistance when they are connected in parallel is (1) 6.33 (2) 2.33 (3) 4.33 (4) 5.33 37. An electron revolves in a circle at the rate of rounds per second. The equivalent current is ) (1) (2) (3) (4) 38. Assertion : In the following circuit the net resistance be‐ tween points and is . Reason : All the resistance are in parallel to each other. (1) Both assertion and reason are cor- rect and reason is the correct explanation of assertion. (2) Both assertion and reason are cor- rect but reason is not the correct explana- tion of assertion. (3) Assertion is cor- rect but reason is incorrect. (4) Assertion is incor- rect but reason is correct. 39. If resistivity of copper is and number of free electrons in copper is Find the mobility. A B cm A B A B 4 : 1 3 : 1 6 : 1 8 : 1 I 1 0.06 0.4 1.5 A 1 2 A 3 4 2 A A 1 8 10 s R − C 10 3Ω 10μF 100μF 1000μF 10000μF 10 Ω, 60 Ω, 100 Ω 200 Ω A 15 V 200 Ω 7.5 × 10 −5 A 7.5 × 10 −4 A 7.5 × 10 −3 A 7.5 × 10 −2 A W V W V V W W I t I = 4 − 0.08t s 2.55 × 10 20 6.25 × 10 20 1.25 × 10 19 5.25 × 10 19 R1 = (10 ± 0.5)Ω R2 = (15 ± 0.5)Ω 10 19 (e = 1.6 × 10 −19C 1.0 A 1.6 A 2.0 A 2.6 A A B r 172 × 10 −8Ω − m 8.5 × 10 28/m3 .