A divider across an ideal rail is to give with nothing connected to its output

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

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

Problem

A divider across an ideal

15.0\,\mathrm{V}

rail is to give

5.0\,\mathrm{V}

with nothing connected to its output. The lower resistor is fixed at

R_2 = 100\,\Omega

, an E12 value; the upper resistor

R_1

runs from the rail to the output. ((a)) Find the value of

R_1

the algebra asks for, then choose between its E12 neighbours

180\,\Omega

and

220\,\Omega

the one that brings the nominal output closer to

5.0\,\mathrm{V}

. State that nominal output. ((b)) Both resistors are bought as five per cent parts. Find the lowest and highest output the divider can give. ((c)) At the nominal values, find the power in each resistor, and choose for each the smallest rating from

0.25

0.5

1

and

2\,\mathrm{W}

that leaves a factor of two in hand.

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