Magnetic Field Due to a Current Through a Solenoid MCQs

Q1. Which of the following best describes osmosis?

• A.The movement of water molecules from a region of high concentration to a region of low concentration through a partially permeable membrane.
• B.The movement of water molecules from a region of low concentration to a region of high concentration through a partially permeable membrane.
• C.The movement of water molecules from a region of high concentration to a region of high concentration through a partially permeable membrane.
• D.The movement of water molecules through a cell membrane without the need for a concentration gradient.

Answer: A. The movement of water molecules from a region of high concentration to a region of low concentration through a partially permeable membrane.

Q2. Consider the following statements about a solenoid: (I) Its field resembles that of a bar magnet. (II) A soft iron core makes an electromagnet. (III) The field inside a long solenoid is zero. Which of the above statement(s) is/are correct?

• A.None of these
• B.Only III
• C.Only I and II
• D.Only I

Answer: C. Only I and II

To see why, recall that Correct: I, II. That fits the listed correct option directly - Correct. Looking at the others: option A) 'None of these' is incorrect: Re-check each statement individually; option B) 'Only III' doesn't hold - Re-check each statement individually. Hence the answer is C) Only I and II.

Q3. A physics student builds a long cylindrical coil carrying 4 A, having 1500 turns spread across 0.3 m; how strong is the interior axial field?

• A.7.54*10^-3 T
• B.2.51*10^-2 T
• C.8.38*10^-2 T
• D.1.26*10^-2 T

Answer: B. 2.51*10^-2 T

Inside a long solenoid B = mu0*n*I with n = N/L = 1500/0.3 = 5000 turns/m. So B = (4*pi*10^-7)*5000*4 = 2.51*10^-2 T.