Tag: physics

Questions Related to physics

Vehicles are streamlined to reduce 

fluid dynamics option b: engineering physics physics

  1. Static friction

  2. Kinetic friction

  3. Fluid friction

  4. Slidingfriction

Show answer
Correct Option: C
Explanation:

Fishes have streamlined shape. So, to reduce the fluid friction, the vehicles are made streamlined.

A good lubricant should be highly

fluid dynamics option b: engineering physics physics

  1. viscous and velocity

  2. non-viscous volatile

  3. viscous and non-volatile

  4. transparent

Show answer
Correct Option: A
Explanation:

A good lubricant generally possesses the following characteristics: A high boiling point and low freezing point (in order to stay liquid within a wide range of temperatures) A high viscosity index. Thermal stability.

Two spheres $A$ and $B$ fall through the same viscous fluid. $A$ and $B$ have the same density and $B$ has the larger radius.
Then,

fluid dynamics option b: engineering physics physics

  1. A has the larger terminal velocity

  2. A and B have the same terminal velocity

  3. B has the larger terminal velocity

  4. Insufficient information is given to reach a conclusion.

Show answer
Correct Option: C
Explanation:

Two spheres $A$ and $B$ fall through the same viscous fluid $A$ and $B$ have  the same density and $B$ has the larger radius the $B$ has the larger terminal velocity.

$\therefore $ Option $C$ is correct.

Ball pen and fountain pen depends respectively on principle of:-

fluid dynamics option b: engineering physics physics

  1. Surface tension and viscosity

  2. Surface tension and gravity

  3. Gravitation and Surface tension

  4. Surface tension and Surface tension

Show answer
Correct Option: A

More viscous oil is used in summer than in winter in motors due to

fluid dynamics option b: engineering physics physics

  1. rise in temperature in summer, the viscosity of oil increases.

  2. rise in temperature in summer, the viscosity of oil decreases.

  3. surface tension of oil decreases.

  4. surface tension of oil increases.

Show answer
Correct Option: B
Explanation:

Due to rise in temperature viscosity of oil decreases in summers. So more viscous oils are used for better lubricant protection.

With the increasing molecular mass of a liquid, the viscosity .

fluid dynamics option b: engineering physics physics

  1. decreases

  2. increases

  3. no effect

  4. all wrong

Show answer
Correct Option: B
Explanation:

With the increasing molecular mass of a liquid, the viscosity increases.
The flow of molecules is inversely proportional to its mass. Hence, liquids with high molecular mass possess greater viscosity.

When cooking oil is heated in a frying pan, the oil moves around in the pan more easily when it is hot. The main reason for this is that with rise in temperature, there is a decrease in

fluid dynamics option b: engineering physics physics

  1. density

  2. surface tension

  3. viscosity

  4. angle of contact

Show answer
Correct Option: C
Explanation:

That is true. The temperature dependence of liquid viscosity is the phenomenon by which liquid viscosity tends to decrease (ore, alternatively, its fluidity tends to increase) as its temperature increase.

The advantage of ac over dc is that:

ac and dc ac vs dc electro-magnetism effects of electric current physics

  1. its generation cost is much less.

  2. it contains more electric energy.

  3. it is free from voltage fluctuations.

  4. it can be transmitted over long distances with minimum power loss.

Show answer
Correct Option: B
Explanation:

Answer is B.

The advantage of AC over DC is that power transmission is simpler under AC, it can be changed in voltage relatively easily using transformers, and that higher power motors can be devised under AC. It contains more electric energy.

Transformer is used for

ac and dc ac vs dc electro-magnetism effects of electric current physics

  1. increasing the voltage.

  2. decreasing the voltage.

  3. both A and B

  4. neither A nor B

Show answer
Correct Option: C
Explanation:

In A.C, voltage can be increased or decreased with the help of a transformer. But in D.C, this cannot be done. Voltage may be increased using a step up transformer and may be decreased using a step down transformer.

State whether the following statement is True or False. 

The induced current produced in a closed coil is always direct current. 

ac and dc ac vs dc electro-magnetism effects of electric current physics

  1. True

  2. False

Show answer
Correct Option: B
Explanation:

Answer is B.

AC electricity alternates back-and-forth in direction 50 times per second, according to the electrical system in the country. The charge at the ends of the wire alternates between negative (-) and positive (+). If the charge is negative (-), that pushes the negatively charged electrons away from that terminal. If the charge is positive (+), the electrons are attracted in that direction. Thus the electricity in the wire moves in one direction for a short while and then reverses its direction when the generator armature is in a different position. But if the split ring commutators are attached to the coil then the current will move in the same direction.