Exam 27: Circuits

In the diagram, the current in the 3- $\Omega$ resistor is 4 A.The potential difference between points 1 and 2 is:

In the circuit shown, both resistors have the same value R.Suppose switch S is initially closed and capacitor C is charged.When switch S is then opened, the circuit has a time constant $\tau$ _a.Conversely, suppose S is initially open and capacitor C is uncharged.When switch S is then closed, the circuit has a time constant $\tau$ _b.The ratio $\tau$ _a/ $\tau$ _b is:

"The sum of the currents into a junction equals the sum of the currents out of the junction" is a consequence of:

A portion of a circuit is shown, with the values of the currents given for some branches.What is the direction and value of the current i?

Four circuits have the form shown in the diagram.The capacitor is initially uncharged and the switch S is open. The values of the emf , resistance and R, and capacitance C for each for the circuits are Rank the circuits according to the current just after switch S is closed least to greatest.

In the diagrams, all light bulbs are identical and all emf devices are identical.In which circuit (I, II, III, IV, V)will the bulbs glow with the same brightness as in circuit X?

Two 110-V light bulbs, one labeled 25 W and the other 100 W, are connected in series to a 110 V source.Then:

In the diagram R₁ > R₂ > R₃.Rank the three resistors according to the current in them, least to greatest.

Suppose the current charging a capacitor is kept constant.Which graph below correctly gives the potential difference V across the capacitor as a function of time?

A certain galvanometer has a resistance of 100 $\Omega$ and requires 1 mA for full scale deflection.To make this into a voltmeter reading 1 V full scale, connect a resistance of:

A 120-V power line is protected by a 15-A fuse.What is the maximum number of 120 V, 500 W light bulbs that can be operated at full brightness from this line?

The emf of a battery is equal to its terminal potential difference:

An emf source is defined in terms of:

In an antique automobile, a 6-V battery supplies a total of 48 W to two identical headlights in parallel.The resistance of each bulb is:

The equivalent resistance between points 1 and 2 of the circuit shown is:

Resistances of 2.0 $\Omega$ , 4.0 $\Omega$ , and 6.0 $\Omega$ and a 24-V battery are all in series.The current in the 2.0 $\Omega$ resistor is:

An initially uncharged capacitor C is connected in series with resistor R.This combination is then connected to a battery of emf V₀.Sufficient time elapses so that a steady state is reached.Which of the following statements is NOT true?

A battery of emf 24 V is connected to a 6.0- $\Omega$ resistor.As a result, current of 3.0 A exists in the resistor.The rate at which energy is being dissipated in the battery is:

A certain capacitor, in series with a resistor, is being charged.At the end of 10 ms its charge is half the final value.The time constant for the process is about:

Four 20- $\Omega$ resistors are connected in series and the combination is connected to a 20-V emf device.The current in any one of the resistors is: