One insulated conductor from a household extension cord has a mass per unit length of $μ.$ A section of this conductor is held under tension between two clamps. A subsection is located in a magnetic field of magnitude $B$ directed perpendicular to the length of the cord. When the cord carries an $AC$ current of $"i"$ at a frequency of $f,$ it vibrates in resonance in its simplest standing-wave vibration state. Determine the relationship that must be satisfied between the separation $d$ of the clamps and the tension $T$ in the cord.
$T=4\mu f^2d^2$
$T=2\mu f^2d^2$
$T=\frac{\mu f^2d^2}{2}$
$T=\frac{\mu f^2d^2}{4}$
Explain which properties are necessary to understand the speed of mechanical waves.
A uniform string oflength $20\ m$ is suspended from a rigid support. A short wave pulse is introduced at its lowest end. It starts moving up the string. The time taken to reach the supports is (take $g= 10 $ $ms^{-2}$ )
$Assertion :$ Two waves moving in a uniform string having uniform tension cannot have different velocities.
$Reason :$ Elastic and inertial properties of string are same for all waves in same string. Moreover speed of wave in a string depends on its elastic and inertial properties only.
A copper wire is held at the two ends by rigid supports. At $50^{\circ} C$ the wire is just taut, with negligible tension. If $Y=1.2 \times 10^{11} \,N / m ^2, \alpha=1.6 \times 10^{-5} /{ }^{\circ} C$ and $\rho=9.2 \times 10^3 \,kg / m ^3$, then the speed of transverse waves in this wire at $30^{\circ} C$ is .......... $m / s$
The speed of a transverse wave passing through a string of length $50 \;cm$ and mass $10\,g$ is $60\,ms ^{-1}$. The area of cross-section of the wire is $2.0\,mm ^{2}$ and its Young's modulus is $1.2 \times 10^{11}\,Nm ^{-2}$. The extension of the wire over its natural length due to its tension will be $x \times 10^{-5}\; m$. The value of $x$ is $...$