Physics Class Test PDF - IARS Academy

IARs ACADEMY CAREER ACADEMY (NEAR PAIKPARA POST OFFICE, 2 MINUTES OFF B.T ROAD) WHATSAPP NO. 8981955470 Date: 12-09-2024 Full marks: 62....

IARs ACADEMY CAREER ACADEMY (NEAR PAIKPARA POST OFFICE, 2 MINUTES OFF B.T ROAD) WHATSAPP NO. 8981955470 Date: 12-09-2024 Full marks: 62. Time: 120 minutes Physics Class Test Section A 𝟐 𝒙 𝟏𝟎 = 20 1. The current in a conductor varies with time 𝑡 𝑎𝑠 𝐼 = 2𝑡 + 3𝑡 2 , 𝑤ℎ𝑒𝑟𝑒 𝐼 𝑖𝑠 𝑖𝑛 𝑎𝑚𝑝𝑒𝑟𝑒 𝑎𝑛𝑑 𝑡 𝑖𝑛 𝑠𝑒𝑐𝑜𝑛𝑑𝑠. The charge flowing through the conductor between t = 2 sec and t = 3 sec is (𝑎)10 𝐶 (𝑏)24 𝐶 (𝑐 )33𝐶 (𝑑) 44 C 2. The ratio of masses of three wires is 1:2:3 and that of their lengths is 3:2:1. If the material of all the wires is same, the ratio of their resistances is (a) 1:1:1 (b) 1:2:3 (c) 9:4:1 (d) 27: 6: 1 3. If the potential difference V applied across a conductor is increased to 2V with its temperature kept constant, then drift velocity of the free electrons will (a) Remain the same (b) Becomes half of its previous value (c) Doubles the initial value (d) Becomes zero 4. A battery is connected to the conductor of non-uniform cross-sectional area. Which of the following quantities/quantity remains constant? (a) Electrical field only (b) Drift velocity and electrical field (c) Electrical field and current (d) Current only 5. The voltage vs current graph for a conductor at two different temperatures are shown in the figure. The relation between 𝑇1 𝑎𝑛𝑑 𝑇2 is (a) 𝑇1 > 𝑇2 (b) 𝑇1 < 𝑇2 (c) 𝑇1 = 𝑇2 (d) 𝑇1 = 2 𝑇2 6. A metallic wire of resistance 12 ohm is bent to form a square. The resistance between two diagonal points will be. (a) 12 ohms (b) 24 ohms (c) 6 ohms (d) 3 ohms 7. The current in the simple series circuit is 5 A. when an additional resistance of 2 Ω is inserted, the current drops to 4 A. the original resistance of the circuit in ohms was (a) 1.25 (b) 8 (c) 10 (d) 20 8. The current I in the given circuit is (a) 1A (b) 6A (c) 3A (d) 12A 9. The current I in the given circuit is (a) 0.1 A (b) 0.3 A (c) 0.2 A (d) 0.4 A  10. An electric motor runs on DC source of emf 200 V and draws a current of 10 A. if the efficiency of the motor be 40 %, then the resistance of the armature is (a) 2 Ω (b) 8 Ω (c) 12 Ω (d) 16 Ω SECTION B 𝟕 𝒙 𝟔 = 42 11. (a) Establish the relation between drift velocity and current flowing through a conductor where symbols have their usual meaning. 3 (b) Define mobility of a charge conductor. 1 (c) A semiconductor has the electron concentration 0.45 𝑥 1012 𝑚−3 and a hole concentration 5 𝑥 1020 𝑚−3. Find its conductivity. Given: electron mobility = 0.135𝑚2𝑣 −1𝑠 −1 and hole mobility = 0.048 𝑚2 𝑣 −1𝑠 −1 and e = 1.6 𝑥 10−19 𝐶𝑜𝑢𝑙𝑜𝑚𝑏. 2 12. (a) What are the factors affecting the resistance of a conductor? hence define resistivity of the conductor. 4 (b) A cylindrical wire is stretched to increase its length by 10 %. Calculate the % increase in its resistance. 2 13. (a)State and explain Ohm’s law. 2 (b) “a metallic conductor is ohmic at smaller current but non ohmic at large current”. Explain the statement with the help of a graph. 2 (c) the resistance of a tungsten filament at 150° C is 133 Ω. What will be its resistance at 500°𝐶. Given the temperature coefficient of tungsten is 0.0045 𝑝𝑒𝑟 °𝐶. 2 14. (a)Two students A and B were asked to pick a resistor of 15 K Ω from the collection of carbon resistor. A picked a resistor with band colours: brown, green and orange while B picked a resistor with band colours: black, green and red. Who picked the correct resistor? 4 (b) what is the difference between resistance and a resistor? 2 15. (a)In a meter bridge the null point is found at a distance of 60 cm from A. if now the resistance of 5 Ω is connected in series with S, the null point occurs at 50 cm. determine the values of S and R. 3 (b) calculate the equivalent resistance between points A and B of the network shown. 3 16. (a) In Fig. shown, a long uniform potentiometer wire AB is having a constant potential gradient along its length. The null points for the two primary cells of emfs 𝐸1 , and 𝐸2 , connected in the manner shown are obtained at a distance of 120 cm and 300 cm from the end A. Find (i) 𝐸1 /𝐸2 and (ii) position of null point for the cell 𝐸1.4 (b) what do you mean by sensitivity of potentiometer? How can we affect sensitivity of a potentiometer? 2 17. (a) A heater coil is rated 100 W, 200 V. It is cut into two identical parts. Both parts are connected together in parallel, to the same source of 200 V. Calculate the energy liberated per second in the new combination. 2 (b) Taking the expression of current in a mixed combination, deduce the relation for maximum current from a mixed combination of identical cells.2 (c) In the circuit as shown, assuming point A to be at zero potential, use Kirchhoff’s law to determine the potential at point B. 2