12th Physics - Book Back Answers - Unit 2 Current Electricity - English Medium Guides

  

 

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Tamil Nadu Board 12th Standard Physics - Unit 2: Book Back Answers and Solutions

    This post covers the book back answers and solutions for Unit 2 from the Tamil Nadu State Board 12th Standard Physics textbook. These detailed answers have been carefully prepared by our expert teachers at KalviTips.com.

    We have explained each answer in a simple, easy-to-understand format, highlighting important points step by step under the relevant subtopics. Students are advised to read and memorize these subtopics thoroughly. Once you understand the main concepts, you’ll be able to connect other related points with real-life examples and confidently present them in your tests and exams.

    By going through this material, you’ll gain a strong understanding of Unit 2 along with the corresponding book back questions and answers (PDF format).

Question Types Covered:

• 1 Mark Questions: Choose the correct answer, Fill in the blanks, Identify the correct statement, Match the following 
• 2 Mark Questions: Answer briefly 
• 3, 4, and 5 Mark Questions: Answer in detail

All answers are presented in a clear and student-friendly manner, focusing on key points to help you score full marks.

All the best, Class 12 students! Prepare well and aim for top scores. Thank you!

I. Multiple choice questions.

1.The following graph shows current versus voltage values of some unknown conductor. What is the resistance of this conductor?

(a) 2 ohm  

(b) 4 ohm

(c) 8 ohm 

(d)1 ohm 

Answer Key: 

(a) 2 ohm 

 

2. A wire of resistance 2 ohms per meteris bent to form a circle of radius 1m. The equivalent resistance between itstwo diametrically opposite points, A and B as shown in the figure is 

(a) π Ω 
(b) $\frac{\mathit{\pi }}{\mathbf{2}}$Ω
(c) 2π Ω
(d) $\frac{\mathit{\pi }}{\mathbf{4}}$Ω 

Answer Key: 

(a) π Ω

 

3. A toaster operating at 240 V has a resistance of 120 Ω. Its power is
a) 400 W 

b) 2 W
c) 480 W 

d) 240 W 

Answer Key:

c) 480 W 

  

4. A carbon resistor of (47 ± 4.7 ) k Ω to be marked with rings of different colours for its identification. The colour code sequence will be
a) Yellow – Green – Violet – Gold
b) Yellow – Violet – Orange – Silver
c) Violet – Yellow – Orange – Silver
d) Green – Orange – Violet - Gold  

Answer Key:

b) Yellow – Violet – Orange – Silver 

 

5. What is the value of resistance of the following resistor?
 

(a)100 k Ω 

(b)10 k Ω
(c) 1k Ω 

(d)1000 k Ω  

Answer Key:

(a)100 k Ω  

 

6. Two wires of A and B with circular cross section are made up of the same material with equal lengths. Suppose ${\mathit{R}}_{\mathit{A}}\mathbf{=}\mathbf{3}{\mathit{R}}_{\mathit{B}}$, then what is the ratio of radius of wire A to that of B?
(a) 3 

(b) $\sqrt{3}$
(c) $\frac{1}{\sqrt{3}}$

(d) $\frac{1}{3}$
Answer Key:

(c) $\frac{1}{\sqrt{3}}$ 

 
7. A wire connected to a power supply of 230 V has power dissipation ${}_{}$P1. Suppose the wire is cut into two equal pieces and connected parallel to the same power supply. In this case power dissipation is ${\mathit{P}}_{\mathbf{2}}$ . The ratio $\frac{{\mathrm{p}}_2}{{\mathrm{p}}_1}$ is
(a)1 

(b) 2
(c) 3 

(d) 4  

Answer Key:

(d) 4  

 

8. In India electricity is supplied for domestic use at 220 V. It is supplied at 110 V in USA. If the resistance of a 60W bulb for use in India is R, the resistance of a 60W bulb for use in USA will be
(a) R 

(b) 2R
(c) $\frac{\mathrm{R}}{4}$
(d) $\frac{\mathrm{R}}{2}$
Answer Key:

(c) $\frac{\mathrm{R}}{4}$ 

 
9. In a large building, there are 15 bulbs of 40 W, 5 bulbs of 100 W, 5 fans of 80 W and 1 heater of 1k W are connected. The voltage of electricmains is 220 V. The maximum capacity of the main fuse of the building will be
(IIT-JEE 2014)
(a) 14 A 

(b) 8 A
(c) 10 A 

(d) 12 A

Answer Key:

(d) 12 A 

 

 10. There is a current of 1.0 A in the circuit shown below. What is the resistance of P?

a) 1.5 Ω

b) 2.5 Ω
c) 3.5 Ω 

d) 4.5 Ω

Answer Key:

c) 3.5 Ω  

 
11. What is the current drawn out from the battery?  

 a) 1A 

b) 2A

c) 3A 

d) 4A

Answer Key:

a) 1A 

   

12. The temperature coefficient of resistance of a wire is 0.00125 per °C. At 20°C, its resistance is 1 Ω. The resistance of the wire will be 2 Ω at
a) 800 °C

b) 700 °C
c) 850 °C 

d) 820 °C

Answer Key:

b) 700 °C 

 
13. The internal resistance of a 2.1 V cell which gives a current of 0.2 A through a resistance of 10 Ω is
a) 0.2 Ω 

b) 0.5 Ω
c) 0.8 Ω 

d) 1.0 Ω

Answer Key:

d) 1.0 Ω 

 
14. A piece of copper and another of germanium are cooled from room temperature to 80 K. The resistance of
a) each of them increases
b) each of them decreases
c) copper increases and germanium decreases
d) copper decreases and germanium increases

Answer Key:

d) copper decreases and germanium increases 

 
15. In Joule’s heating law, when R and t are constant, if the H is taken along the y axis and ${\mathit{I}}^{\mathbf{2}}$ along the x axis, the graph is
a) straight line 

b) parabola
c) circle 

d) ellipse 

Answer Key:

a) straight line  

II. Short answer questions.

12th Physics

III. Long answer questions. 

12th Physics

IV. Exercises.   

12th Physics