Figure 19.7 Measuring voltage with a voltmeter.Current is the same for any resistors in series with one another. So, if you’re going to measure the current
through a resistor, the ammeter must be in series with that resistor. In Figure 19.8 , ammeter A 1 measures
the current through resistor R 1 , while ammeter A 2 measures the current through resistor R 2 .
Figure 19.8 Measuring current with an ammeter.As an exercise, ask yourself, is there a way to figure out the current in the other three resistors based only
on the readings in these two ammeters? The answer is in the footnote.^2
RC Circuits: Steady-State Behavior
When you have both resistors and capacitors in a circuit, the circuit is called an “RC circuit.” If you
remember, we introduced capacitors in Chapter 18 , when we talked about charged, parallel plates.
The simplest problems with capacitors in circuits involve “steady-state behavior.” This just means
that the circuit has been connected for a while. In these cases, the only thing you’ll generally need to
worry about is how to deal with capacitors in series and in parallel.
When capacitors occur in series, you add them inversely. The charge stored on each capacitor in
series must be the same.
For the circuit in Figure 19.9 , the equivalent capacitance is C (^) eq = 1.5 μF.