Tag: physics

Questions Related to physics

What make(s) water conducting?

physics chemical effects of electric current does liquid conduct electricity? liquids conduct electricity do liquids conduct electricity?

  1. Salts

  2. Hydrogen

  3. Oxygen

  4. None of the above

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Correct Option: A
Explanation:

Salts makes water conducting.

Most liquids that conduct electricity are solutions of :

physics chemical effects of electric current does liquid conduct electricity? liquids conduct electricity do liquids conduct electricity?

  1. acids

  2. bases

  3. salts

  4. all of the above

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Correct Option: D
Explanation:

Most liquids that conduct electricity are solutions of acids, bases ,and salts (because the  solutions of acids, bases or salts are conducting in nature. They allow the current to pass through

Which of the following is free of salts?

physics chemical effects of electric current does liquid conduct electricity? liquids conduct electricity do liquids conduct electricity?

  1. Distilled water

  2. Sea water

  3. Tap water

  4. All of the above

Show answer
Correct Option: A
Explanation:

Distilled water is free of salts.

Which of the following is used to detect the current?

physics chemical effects of electric current does liquid conduct electricity? liquids conduct electricity do liquids conduct electricity?

  1. Tester

  2. LED

  3. Compass needle

  4. All of the above

Show answer
Correct Option: D
Explanation:

Tester, LED and compass needle, all of them are used to detect electric current.

Electric circuit provides a complete path for :

physics chemical effects of electric current does liquid conduct electricity? liquids conduct electricity do liquids conduct electricity?

  1. solution to flow

  2. metal to flow

  3. neutron to flow

  4. current to flow

Show answer
Correct Option: D
Explanation:

Electric circuit provides a complete path for current to flow.

Small amounts of mineral salts present naturally in water are :

physics chemical effects of electric current does liquid conduct electricity? liquids conduct electricity do liquids conduct electricity?

  1. harmful for human health

  2. not at all useful for humans

  3. beneficial for human health

  4. none of the above

Show answer
Correct Option: C
Explanation:

Small amounts of mineral salts present naturally in water are beneficial for human health.

Water obtained from which of the following sources is a good conductor of electricity?

physics chemical effects of electric current does liquid conduct electricity? liquids conduct electricity do liquids conduct electricity?

  1. Tap

  2. Ponds

  3. Wells

  4. All of the above

Show answer
Correct Option: D
Explanation:

The water that we get from sources such as taps, hand pumps, wells and ponds is not pure. It may contain several salts dissolved in it. Small amounts of mineral salts are naturally present in it. This water is thus a good conductor of electricity.

Which of the following is a good conductor of electricity?

physics chemical effects of electric current does liquid conduct electricity? liquids conduct electricity do liquids conduct electricity?

  1. Sugar solution

  2. Oil

  3. Distilled water

  4. Tap water

Show answer
Correct Option: D
Explanation:

The water that we get from sources such as taps, hand pumps, wells and ponds is not pure. It may contain several salts dissolved in it. Small amounts of mineral salts are naturally present in it. This water is thus a good conductor of electricity.

An electric dipole of moment $ \vec { p } $ is placed in a uniform electric field$\vec { E }$ . Then
(i) The torque on the dipole is $\vec { p } \times \vec { E } $.
(ii) The potential energy of the system is $\vec { p } \cdot \vec { E } $.
(iii) The resultant force on the dipole is zero.
Choose the correct option.

torque on a dipole in a uniform electric field electric dipole electric charges and fields electrostatics physics

  1. (i), (ii) and (iii) are correct

  2. (i) and (iii) are correct and (ii) is wrong

  3. Only (i) is wrong

  4. (i) and (ii) are correct and (iii) is wrong

Show answer
Correct Option: A
Explanation:

In a uniform electric field, $\vec { E } $, dipole experiences a torque $\vec { \tau  } $ given by $\vec { \tau  } =\vec { p } \times \vec { E } $ but experiences no force. The potential energy of the dipole in a uniform electric field $\vec { E } $ is $U=-\vec { p } .\vec { E } $

An electric dipole of length 20 cm having $\pm3 \times { 10 }^{ -3 }$ C charge placed at 60 with respect to a uniform electric field experiences a torque of magnitude 6 N m. the potential energy of the dipole is:

torque on a dipole in a uniform electric field electric dipole electric charges and fields electrostatics physics

  1. -2$\sqrt { 3 }$ J

  2. 5$\sqrt { 3 }$ J

  3. -3$\sqrt { 2 }$ J

  4. 3$\sqrt { 5 }$ J

Show answer
Correct Option: A
Explanation:

Here,

Length of dipole $2a= 20\ cm=0.2\ m$
Charge, $q= \pm 3\times 10^{-3}\ C$,             $\theta=60^o$
Torque, $\tau=6\ Nm$
As, $\tau=pEsin\ \theta$
or $E=\dfrac{\tau}{psin \theta}= \dfrac{\tau}{q(2a)sin \theta}(\because p=q(2a)$

$\therefore E=\dfrac{6}{3\times 10^{-3}\times 20 \times 10^{-2} \times sin\ 60^o}= \dfrac{10^5}{5\sqrt 3} NC^{-1}$

Potential energy of dipole, $U=-pEcos \theta=-q(2a) E cos \theta $

$\implies U= -3\times 10^{-3}(20 \times 10^{-2} )\dfrac{10^5}{5\sqrt 3} cos 60^o= -2\sqrt 3\ J$