An ideal source is connected through to a node

PHYSICS · Multi-part · Fermi University Physics · Electronics, Instrumentation & Communication · Circuit foundations and passive networks · Sensors, detectors and experimental instrumentation

Electronics for Measurement, Ch The resistive network: two laws, one equivalent and the loading error

Problem

An ideal

20.0\,\mathrm{V}

source is connected through

R_1=2.0\,\mathrm{k}\Omega

to a node

A

, and

R_2=8.0\,\mathrm{k}\Omega

runs from

A

to ground. The output terminals are

A

and ground. A technician says: "To find the Thevenin resistance without disconnecting the battery, I imagine the source suppressed, which just leaves it removed from the circuit, so

R_1

and

R_2

are left in series as seen from the terminals:

R_{\rm th}=R_1+R_2=10.0\,\mathrm{k}\Omega

." ((a)) Find the true

R_{\rm th}

from an open-circuit and a short-circuit test, and say what is wrong with the technician's reasoning. ((b)) A moving-coil voltmeter of input resistance

4.0\,\mathrm{k}\Omega

is then connected across

A

-ground. Predict its reading.

Browse the problem library