State Lenz’s law for electromagnetic induction.
As shown in Fig. 8.1, two insulated-wire coils are wound around an iron bar. The current $I_1$ in coil 1 changes with time $t$ as displayed in Fig. 8.2.
The way $I_1$ varies with $t$ may be written as $I_1 = X \sin Yt$, where $X$ and $Y$ are constants. Use Fig. 8.2 to find $X$ and $Y$. Include units in your answers.
Current in coil 1 produces a magnetic field in the iron bar. Assume the flux density of this magnetic field is proportional to $I_1$. An alternating electromotive force (e.m.f.) is induced across coil 2. The p.d. across coil 2 is measured with the voltmeter and has a root-mean-square (r.m.s.) value of $4.6\ \text{V}$. On Fig. 8.3, sketch a line to show how $V_2$ varies with $t$ from $t = 0$ to $t = 0.08\ \text{s}$.
Use the laws of electromagnetic induction to explain why your line in (b)(ii) has this shape.
Use Fig. 8.2 to find the values of $X$ and $Y$. Include units in your answers.
Current in coil 1 creates a magnetic field in the iron bar. Take the flux density of this magnetic field to be proportional to $I_1$. An alternating electromotive force (e.m.f.) appears across coil 2. The p.d. across coil 2 is measured with the voltmeter and has a root-mean-square (r.m.s.) value of $4.6\,\text{V}$. On Fig. 8.3, sketch a line to show how $V_2$ varies with $t$ from $t = 0$ to $t = 0.08\,\text{s}$.
Use the laws of electromagnetic induction to explain the shape of your line in (c)(ii).