21.5 Exercise 8

(a) What is the unknown $\text{emf}_{\text{x}}$ in a potentiometer that balances when $R_{\text{x}}$ is $\text{10} . 0 \Omega$, and balances when $R_{\text{s}}$ is $\text{15} . 0 \Omega$ for a standard 3.000-V emf? (b) The same $\text{emf}_{\text{x}}$ is placed in the same potentiometer, which now balances when $R_{\text{s}}$ is $\text{15} . 0 \Omega$ for a standard emf of 3.100 V. At what resistance $R_{\text{x}}$ will the potentiometer balance?