A single rectangular coil of cross-sectional area A is placed with its plane vertical and two of its sides horizontal in a uniform horizontal magnetic field of flux B. When the coil carries a current I, the couple required to hold it with its plane at an angle to the direction of the field is directly proportional to ____.

• A.Cross-sectional area A
• B.Square of flux density
• C.Square root of I
• D.None of the above