Chapter 28: Fundamentals of Circuits

A circuit you’re building needs an ammeter that goes from $0\mathrm{mA}$to a full-scale reading of $50\mathrm{mA}$. Unfortunately, the only ammeter in the storeroom goes from $0\mathrm{\mu A}$to a full-scale reading of only $500\mathrm{\mu A}$. Fortunately, you’ve just finished a physics class, and you realize that you can make this ammeter work by putting a resistor in parallel with it, as shown in FIGURE P28.57. You’ve measured that the resistance of the ammeter is$50\Omega$, not the$0\Omega$of an ideal ammeter.

a. What value of R must you use so that the meter will go to full scale when the current I is$50\mathrm{mA}$?

b. What is the effective resistance of your ammeter?

For the circuit shown in FIGURE P28.58, find the current through and the potential difference across each resistor. Place your results in a table for ease of reading.

For the circuit shown in FIGURE $28.59$, find the current through and the potential difference across each resistor. Place your results in a table for ease of reading.

What is the magnitude of the potential difference across each resistor in FIGURE $EX28.6$?

Rank in order, from largest to smallest, the powers $P_{\mathrm{a}}$to $P_{\mathrm{d}}$dissipated by the four resistors in FIGURE

For the circuit shown in FIGURE $P28.60$, find the current through and the potential difference across each resistor. Place your results in a table for ease of reading.

For the circuit shown in FIGURE P28.60, find the current through and the potential difference across each resistor. Place your results in a table for ease of reading.

What is the current through the 20 Ω resistor in FIGURE P28.61?

For the circuit shown in FIGURE P28.62, find the current through and the potential difference across each resistor. Place your results in a table for ease of reading.

What is the current through the $10\Omega$resistor in $figureP28.63$? Is the current from left to right or right to left?