MCQOPTIONS

Explore topic-wise MCQs in Physics.

This section includes 21 Mcqs, each offering curated multiple-choice questions to sharpen your Physics knowledge and support exam preparation. Choose a topic below to get started.

1.	A body cools in a surrounding which is at a constant temperature of \[{{\theta }_{0}}\]. Assume that it obeys Newton's law of cooling. Its temperature \[\theta \] is plotted against time t. Tangents are drawn to the curve at the points \[P(\theta ={{\theta }_{1}})\] and \[Q(\theta ={{\theta }_{2}})\]. These tangents meet the time axis at angles of \[{{\varphi }_{2}}\]and \[{{\varphi }_{1}}\], as shown
A.	\[\frac{\tan \,{{\varphi }_{2}}}{\tan \,{{\varphi }_{1}}}=\frac{{{\theta }_{1}}-{{\theta }_{0}}}{{{\theta }_{2}}-{{\theta }_{0}}}\]
B.	\[\frac{\tan \,{{\varphi }_{2}}}{\tan \,{{\varphi }_{1}}}=\frac{{{\theta }_{2}}-{{\theta }_{0}}}{{{\theta }_{1}}-{{\theta }_{0}}}\]
C.	If assertion is true but reason is false.
D.	\[\frac{\tan \,{{\varphi }_{1}}}{\tan \,{{\varphi }_{2}}}=\frac{{{\theta }_{2}}}{{{\theta }_{1}}}\]
Answer» C. If assertion is true but reason is false.

2.	A composite metal bar of uniform section is made up of length 25 cm of copper, 10 cm of nickel and 15 cm of aluminium. Each part being in perfect thermal contact with the adjoining part. The copper end of the composite rod is maintained at \[{{100}^{o}}C\] and the aluminium end at \[{{0}^{o}}C\]. The whole rod is covered with belt so that there is no heat loss occurs at the sides. If \[{{K}_{\text{Cu}}}=2{{K}_{Al}}\] and \[{{K}_{Al}}=3{{K}_{\text{Ni}}}\], then what will be the temperatures of \[Cu-Ni\] and \[Ni-Al\] junctions respectively
A.	\[{{23.33}^{o}}C\] and \[A\]
B.	\[{{83.33}^{o}}C\] and \[{{20}^{o}}C\]
C.	\[\hat{i}+\hat{j}\]
D.	\[{{30}^{o}}C\] and \[{{50}^{o}}C\]
Answer» C. \[\hat{i}+\hat{j}\]

3.	One end of a copper rod of uniform cross-section and of length 3.1 m is kept in contact with ice and the other end with water at 100°C. At what point along it's length should a temperature of 200°C be maintained so that in steady state, the mass of ice melting be equal to that of the steam produced in the same interval of time. Assume that the whole system is insulated from the surroundings. Latent heat of fusion of ice and vaporisation of water are 80 cal/gm and 540 cal/gm respectively
A.	40 cm from 100°C end
B.	40 cm from 0°C end
C.	\[5\sqrt{2}\]
D.	125 cm from 0°C end
Answer» B. 40 cm from 0°C end

4.	Ice starts forming in lake with water at \[{{0}^{o}}C\] and when the atmospheric temperature is \[-{{10}^{o}}C\]. If the time taken for 1 cm of ice be 7 hours, then the time taken for the thickness of ice to change from 1 cm to 2 cm is [NCERT 1971; MP PMT/PET 1988; UPSEAT 1996]
A.	7 hours
B.	14 hours
C.	\[R\sqrt{2}\]
D.	More than 7 hours
Answer» E.

5.	The layers of atmosphere are heated through [MP PET 1986]
A.	Convection
B.	Conduction
C.	\[-K{{a}^{2}}\]
D.	(b) and (c) both
Answer» B. Conduction

6.	For proper ventilation of building, windows must be open near the bottom and top of the walls so as to let pass
A.	In more air
B.	In cool air near the bottom and hot air out near the roof
C.	2
D.	Out hot air near the roof
Answer» C. 2

7.	If a liquid is heated in weightlessness, the heat is transmitted through [RPMT1996]
A.	Conduction
B.	Convection
C.	If assertion is true but reason is false.
D.	Neither, because the liquid cannot be heated in weightlessness
Answer» B. Convection

8.	The coefficient of thermal conductivity depends upon [MP PET/PMT 1984; AFMC 1996; Orissa JEE 2005]
A.	Temperature difference of two surfaces
B.	Area of the plate
C.	If assertion is true but reason is false.
D.	Material of the plate
Answer» E.

9.	Heat current is maximum in which of the following (rods are of identical dimension) [Orissa JEE 2003]
A.
B.
C.	If assertion is true but reason is false.
D.
Answer» B.

10.	One end of a metal rod of length 1.0 m and area of cross section \[100c{{m}^{2}}\] is maintained at \[{{100}^{o}}C.\]If the other end of the rod is maintained at \[{{0}^{o}}C\], the quantity of heat transmitted through the rod per minute is (Coefficient of thermal conductivity of material of rod =100W/m-K) [EAMCET (Engg.) 2000]
A.	\[3\times {{10}^{3}}J\]
B.	\[6\times {{10}^{3}}J\]
C.	\[90{}^\circ \]
D.	\[12\times {{10}^{3}}J\]
Answer» C. \[90{}^\circ \]

11.	On a cold morning, a metal surface will feel colder to touch than a wooden surface because [AIIMS 1998]
A.	Metal has high specific heat
B.	Metal has high thermal conductivity
C.	20 N
D.	Metal has low thermal conductivity
Answer» C. 20 N

12.	Two spheres of different materials one with double the radius and one-fourth wall thickness of the other, are filled with ice. If the time taken for complete melting ice in the large radius one is 25 minutes and that for smaller one is 16 minutes, the ratio of thermal conductivities of the materials of larger sphere to the smaller sphere is [EAMCET 1991]
A.	4 : 5
B.	5 : 4
C.	18
D.	1 : 25
Answer» E.

13.	If the radius and length of a copper rod are both doubled, the rate of flow of heat along the rod increases
A.	4 times
B.	2 times
C.	\[\text{6}0{}^\circ \]
D.	16 times
Answer» C. \[\text{6}0{}^\circ \]

14.	Two rods of same length and material transfer a given amount of heat in 12 seconds, when they are joined end to end. But when they are joined lengthwise, then they will transfer same heat in same conditions in [BHU 1998; UPSEAT 2002]
A.	24 s
B.	3 s
C.	132 km
D.	48s
Answer» E.

15.	The temperature gradient in a rod of 0.5 m long is \[{{80}^{o}}C/m\]. If the temperature of hotter end of the rod is\[{{30}^{o}}C\], then the temperature of the cooler end is
A.	\[{{40}^{o}}C\]
B.	\[-{{10}^{o}}C\]
C.	\[-4\hat{i}+6\hat{j}\]
D.	\[{{0}^{o}}C\]
Answer» C. \[-4\hat{i}+6\hat{j}\]

16.	In variable state, the rate of flow of heat is controlled by
A.	Density of material
B.	Specific heat
C.	40 m/s S?W
D.	All the above factors
Answer» E.

17.	The ratio of thermal conductivity of two rods of different material is 5 : 4. The two rods of same area of cross-section and same thermal resistance will have the lengths in the ratio [MP PET 1984; BVP 2003]
A.	4 : 5
B.	9 : 1
C.	\[\text{135}{}^\circ \]
D.	5 : 4
Answer» E.

18.	Assertion : It is hotter over the top of a fire than at the same distance on the sides. Reason : Air surrounding the fire conducts more heat upwards. [AIIMS 2003]
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	\[\sqrt{{{A}^{2}}+{{B}^{2}}-2AB\sin \theta }\]
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» D. If the assertion and reason both are false.

19.	Assertion : Two thin blankets put together are warmer than a single blanket of double the thickness. Reason : Thickness increases because of air layer enclosed between the two blankets.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	\[\text{12}0{}^\circ \]
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» D. If the assertion and reason both are false.

20.	Assertion : Snow is better insulator than ice. Reason : Snow contain air packet and air is good insulator of heat.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	\[{{45}^{o}}\]
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

21.	Assertion : The radiation from the sun?s surface varies as the fourth power of its absolute temperature. Reason : The sun is not a black body. [AIIMS 1999]
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	\[\frac{ML{{\omega }^{2}}}{4}\]
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» D. If the assertion and reason both are false.