Tag: physics

Quizzes (598) Questions (13441)

Questions Related to physics

Multiple choice ac voltage applied to a series lr circuit lr circuit phase relations between alternating voltage and alternating current in different types of alternating current circuits and phasor diagram electromagnetic induction and alternating currents physics

A $0.21\space H$ inductor and a $12\Omega$ resistance are connected in series to a $220\space V, 50\space Hz$ ac source. The current in the circuit is :

  1. $\displaystyle\frac{220}{\sqrt{4400}}A$

  2. $\displaystyle\frac{22}{3\sqrt5}A$

  3. $\displaystyle\frac{220}{\sqrt{4550}}A$

  4. $\displaystyle\frac{22}{5\sqrt3}A$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$ X _L = L 2 \pi f = 0.21 \times 314 \Omega $
$ R = 12 \Omega $
$ I = \dfrac{ 220}{ \sqrt{ X _L^2 + R^2 } } = 3.28 = \dfrac{22}{3\sqrt{5}} A  $

Multiple choice ac voltage applied to a series lr circuit lr circuit phase relations between alternating voltage and alternating current in different types of alternating current circuits and phasor diagram electromagnetic induction and alternating currents physics

An A.C voltage $V=5\cos { \left( 1000t \right) V } $ is applied to a L-R series circuit of inductance $3mH$ and resistance $4\Omega$. The value of maximum current in the circuit is  _______ A

  1. $0.8$

  2. $1.0$

  3. $\cfrac{5}{7}$

  4. $\cfrac { 5 }{ \sqrt { 7 } } $
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$V=5\cos { \left( 1000t \right) V } $

The standard equation for the voltage is:
$V={ V } _{ 0 }\cos { \omega t } $

So, from the equation, ${ V } _{ 0 }=5volt;\omega =1000rad/s$
$L=3\times { 10 }^{ -3 }H,R=4\Omega $

Maximum current $10=\cfrac { { V } _{ 0 } }{ Z } \quad $
$10=\cfrac { 5 }{ \sqrt { { \omega  }^{ 2 }{ L }^{ 2 }+{ R }^{ 2 } }  } =\cfrac { 5 }{ 5 } =1A\quad \quad $

Multiple choice physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

The surface of the head of a match stick and sides of a match box are deliberately made rough to:

  1. increase friction

  2. decrease friction

  3. increase amount of heat

  4. decrease amount of heat
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The rough surface will increase the friction and so the rough surface of match box and match stick will produce more friction which helps in firing the stick easily.  

Multiple choice physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

Correct air pressure in our vehicle tyres help to reduce:

  1. static friction

  2. sliding friction

  3. rolling friction

  4. all of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Correct air pressure helps in reducing deformation of the tyre and also provide an air cushion to reduce rolling friction. 


Option C is correct.

Multiple choice physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

Friction is minimised by using

  1. Wheels and balI bearings

  2. More number of tyres in a car

  3. Rough surfaces

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Answer is A.

Bearings reduce friction by providing smooth metal balls or rollers, and a smooth inner and outer metal surface for the balls to roll against. These balls or rollers 'bear' the load, allowing the device to spin smoothly.
The concept behind a bearing is very simple. Things roll better than they slide. The wheels on our car are like big bearings. If we had something like skis instead of wheels, our car would be a lot more difficult to push down the road.
That is because when things slide, the friction between them causes a force that tends to slow them down. But if the two surfaces can roll over each other, the friction is greatly reduced.

Multiple choice physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

powder sprinkled on a carrom board

  1. magnifies friction.

  2. reduces friction.

  3. removes friction.

  4. does not affect friction.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The carom board may sometimes be very rough. Sprinkling powder on a microscopic level, the powder particles offer rolling friction to the striker because of which the striker can be used for smooth and fast play.

Multiple choice physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

The force of friction on a static body ________ , if It is on a rough surface then.

  1. is always zero

  2. may be gravity.

  3. may be zero

  4. both B & C
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The force of friction f is always opposite the direction the object that is moving . If the object would move, then the direction of the force of friction f will be opposite the movement. If the object would not move when there is no friction, then the force of friction is zero.Hence, though the surfaces of the object are rough the force of friction can be zero if the object would not move.

Multiple choice physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

Powder is used in carrom board for

  1. Increasing friction

  2. Decreasing friction

  3. Decoration

  4. Fragrance
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Answer is B.

The surface well powdered to stay away from harm to board surface due to scratch.It reduces the friction and helps in smoothing of the board and thereby allows the carom coins to go through in that flow which helps in fast play.
Powder is used in carom board for decreasing friction.