Neon signs require $12 \mathrm{kV}$ for their operation. To operate from a $240\mathrm{V}$ line, what must be the ratio of secondary to primary turns of the transformer? What would the voltage output be if the transformer were connected in reverse?

Calculate the peak output voltage of a simple generator whose square armature windings are $5.50 \mathrm{~cm}$ on a side; the armature contains $125$ loops and rotates in a field of $0.200 \mathrm{~T}$ at a rate of $120 \mathrm{rev} / \mathrm{s}$.

Calculate the peak output voltage of a simple generator whose square armature windings are 6.60 cm on a side; the armature contains 155 loops and rotates in a field of 0.200 T at a rate of 120 rev/s.

A circular loop in the plane of the paper lies in a $0.65~\mathrm{T}$ uniform magnetic field pointing into the paper. The loop's diameter changes from $20.0 \mathrm{~cm}$ to $8.0 \mathrm{~cm}$ in $0.50 \mathrm{~s}$. What is the average induced current if the coil resistance is $2.5 \Omega$ ?

A circular loop in the plane of the paper lies in a $0.65~\mathrm{T}$ uniform magnetic field pointing into the paper. The loop's diameter changes from $20.0 \mathrm{~cm}$ to $8.0 \mathrm{~cm}$ in $0.50 \mathrm{~s}$. What is the magnitude of the average induced emf?

A circular loop in the plane of the paper lies in a $0.65~\mathrm{T}$ uniform magnetic field pointing into the paper. The loop's diameter changes from $20.0 \mathrm{~cm}$ to $8.0 \mathrm{~cm}$ in $0.50 \mathrm{~s}$. What is the direction of the induced current?

Suppose that the U-shaped conductor and connecting rod in Fig. 29-12a are oriented vertically (but still in contact) so that the rod is falling due to the gravitational force. Find the terminal speed of the rod if it has mass $m=3.6$ grams, length $\ell=18 \mathrm{~cm}$, and resistance $R=0.0013 \Omega$. It is falling in a uniform horizontal field $B=0.060 \mathrm{~T}$. Neglect the resistance of the U-shaped conductor.

In Fig. 29-12a, the rod moves to the right with a speed of $1.3 \mathrm{~m} / \mathrm{s}$ and has a resistance of $2.5 \Omega$. The rail separation is $\ell=25.0 \mathrm{~cm}$. The magnetic field is $0.35 \mathrm{~T}$, and the resistance of the U-shaped conductor is $25.0 \Omega$ at a given instant. Calculate (a) the induced emf.

The magnetic field perpendicular to a single 13.2-cm-diameter circular loop of copper wire decreases uniformly from 0.750 T to zero. If the wire is 2.25 mm in diameter, how much charge moves past a point in the coil during this operation?

The magnetic flux through each loop of a $75$ - loop coil is given by $\left(9.6 t-0.51 t^3\right) \times 10^{-2} \mathrm{~T} \cdot \mathrm{m}^2$, where the time $t$ is in seconds. $(a)$ Determine the emf $\mathscr{E}$ as a function of time. $(b)$ What is $\mathscr{E}$ at $t=1.0 \mathrm{~s}$ and $t=4.0 \mathrm{~s}$ ?

The magnetic flux through each loop of a 75 -loop coil is given by $\left(8.8 t-0.51 t^3\right) \times 10^{-2} \mathrm{~T} \cdot \mathrm{m}^2$, where the time $t$ is in seconds (a) Determine the emf $\mathscr{E}$ as a function of time.

The magnetic field perpendicular to a single $13.2~\mathrm{cm}$ diameter circular loop of copper wire decreases uniformly from $0.760 \mathrm{~T}$ to zero. If the wire is $2.25 \mathrm{~mm}$ in diameter, how much charge moves past a point in the coil during this operation?

The magnetic flux through each loop of a $75$ - loop coil is given by $\left(9.6 t-0.51 t^3\right) \times 10^{-2} \mathrm{~T} \cdot \mathrm{m}^2$, where the time $t$ is in seconds. $(a)$ Determine the emf $\mathscr{E}$ as a function of time.

The magnetic flux through a coil of wire containing two loops changes from -50 Wb to +38 Wb in 0.42 s. What is the emf induced in the coil?