University:
Cypress College
Course:
PHYS 201 C | College Physics I
Academic year:

2021
Views:

24

Pages:

20
Author:

NikkiP24

Chapter 11: Electric Current Through Conductors EXERCISES [PAGES 219-220) Exercises | Q1.) | Page 219 Choose the correct alternative. You are given four bulbs of 25 W. 40 W, 60 W, and 100 W of power, all operating at 230 V. Which of them has the lowest resistance? 1. 25 W 2. 40 W 3. 60 W 4. 100 W SOLUTION 100 W Explanation: P = V2 R Since all the bulbs are operating at the same volt. Pa 1 R The bulb with the highest power will have the lowest resistance. Le., 100 W bulb Exercises | Q1. (1) | Page 219 Choose the correct alternative. Which of the following is an ohmic conductor? 1. transistor 2. vacuum tube 3. electrolyte 4. nichrome wire SOLUTION Nichrome wire Exercises | Q1. (iii) | Page 219 Choose the correct alternative. A rheostat is used 1. to bring on a known change of resistance in the circuit to alter the current 2. to continuously change the resistance in any arbitrary manner and thereby alter the current 3. to make and break the circuit at any instant 4. neither to alter the resistance nor the current SOLUTION To continuously change the resistance in any arbitrary manner and thereby alter the current Exercises | Q1. (iv) | Page 219 Choose the correct alternative. The wire of length Land resistance R is stretched so that its radius of cross-section is halved. What is its new resistance? 1. 5R 2. 8R 3. 4R 4. 16R SOLUTION 16R Explanation: letr, and 1, be their initial radius of the wire and ra and la be their final radius of the wire. Initial volume=Final volume Since r2 = ance. R = A Resistance, R = pl R 12 h 4 2 (1) 1 16 R2 = 16 R1 Exercises | Q1. (v) | Page 219 Choose the correct alternative. Masses of three pieces of wires made of the same metal are in the ratio 1:3:5 and their lengths are in the ratio 5:3:1. The ratios of their resistances are 1. 1:3:5 2. 5:3:1 3. 1:15:125 4. 125:15:1 SOLUTION 125:15:1 Explanation: plx1 pl R = pl A Ax1 V Since, V = m d m/d 12 Ra- m R1 R2 R3 = my