Physics 9702 · AS & A Level · Practical circuits

Practical circuits — practice question

A battery with electromotive force (e.m.f.) $V$ and negligible internal resistance is connected to a $1\,\text{k}\Omega$ resistor, as shown. A student tries to measure the potential difference (p.d.) between points P and Q using two voltmeters, one after the other. The first voltmeter has a resistance of $1\,\text{k}\Omega$ and the second voltmeter has a resistance of $1\,\text{M}\Omega$. What are the readings of the voltmeters?

  • Areading on voltmeter with $1\,\text{k}\Omega$ resistance: $\frac{V}{2}$; reading on voltmeter with $1\,\text{M}\Omega$ resistance: $\frac{V}{2}$
  • Breading on voltmeter with $1\,\text{k}\Omega$ resistance: $\frac{V}{2}$; reading on voltmeter with $1\,\text{M}\Omega$ resistance: $V$
  • Creading on voltmeter with $1\,\text{k}\Omega$ resistance: $V$; reading on voltmeter with $1\,\text{M}\Omega$ resistance: $\frac{V}{2}$
  • Dreading on voltmeter with $1\,\text{k}\Omega$ resistance: $V$; reading on voltmeter with $1\,\text{M}\Omega$ resistance: $V$

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