State Kirchhoff’s second law for a circuit.
A battery with electromotive force (e.m.f.) $4.0\ \text{V}$ and internal resistance $0.35\ \Omega$ is joined to a uniform resistance wire XY and a fixed resistor of resistance $R$, as shown in Fig. 5.1. Wire XY has resistance $0.90\ \Omega$. The potential difference across wire XY is $1.8\ \text{V}$. Calculate:
current in wire XY
the quantity of free electrons that pass a point in the battery in a time of $45\ \text{s}$
the resistance $R$.
A cell with e.m.f. $1.2\ \text{V}$ is connected to the circuit in (b), as shown in Fig. 5.2. Point $P$ is shifted along wire XY. The galvanometer shows zero when distance XP is $0.30\ \text{m}$. Calculate:
Calculate the full length $L$ of wire XY.
The fixed resistor is replaced by another fixed resistor with resistance greater than $R$. State and explain what change, if any, must be made to the position of $P$ on wire XY so that the galvanometer reading is zero.