27. Resistors & DC Circuits

Which of the following best describes an electrical current?

The electron beam inside an old television picture tube is 0.40 mm in diameter and carries a current of 50 μA. This electron beam impinges on the inside of the picture tube screen. How many electrons strike the screen each second?

Which statement correctly describes the formation of an $\mathrm{electric current}$?

Which of the following best describes how a switch functions in an electrical circuit?

Which type of electric current is most commonly supplied to homes for powering appliances?

Which of the following is the correct unit for measuring electric current?

Which of the following is the standard unit of measurement for electric current?

A 4.5-V battery is connected to a bulb whose resistance is 2.3 Ω. How many electrons leave the battery per minute?

If a wire delivers a charge $Q$ in a time $t$ with current $I$, what is the current in a second wire that delivers twice as much charge ($2Q$) in half the time ($\frac{t}{2}$)?

You've decided to protect your house by placing a 5.0-m-tall iron lightning rod next to the house. The top is sharpened to a point and the bottom is in good contact with the ground. From your research, you've learned that lightning bolts can carry up to 50 kA of current and last up to 50 μs. How much charge is delivered by a lightning bolt with these parameters?

An ammeter has a sensitivity of 35, 000Ω /V. What current in the galvanometer produces full-scale deflection?

The current in a 2.0 mm x 2.0 mm square aluminum wire is 2.5 A. What are (a) the current density and (b) the electron drift speed?