9.1 Electrical Current

Handheld calculators often use small solar cells to supply the energy required to complete the calculations needed to complete your next physics exam. The current needed to run your calculator can be as small as 0.30 mA. How long would it take for 1.00 C of charge to flow from the solar cells? Can solar cells be used, instead of batteries, to start traditional internal combustion engines presently…

Circuit breakers in a home are rated in amperes, normally in a range from 10 amps to 30 amps, and are used to protect the residents from harm and their appliances from damage due to large currents. A single 15-amp circuit breaker may be used to protect several outlets in the living room, whereas a single 20-amp circuit breaker may be used to protect the refrigerator in the kitchen. What can you de…

Can a wire carry a current and still be neutral—that is, have a total charge of zero? Explain.

When working with high-power electric circuits, it is advised that whenever possible, you work “one-handed” or “keep one hand in your pocket.” Why is this a sensible suggestion?

A Van de Graaff generator is one of the original particle accelerators and can be used to accelerate charged particles like protons or electrons. You may have seen it used to make human hair stand on end or produce large sparks. One application of the Van de Graaff generator is to create X-rays by bombarding a hard metal target with the beam. Consider a beam of protons at 1.00 keV and a current of…

How many electrons flow through a point in a wire in 3.00 s if there is a constant current of $I = 4.00 \text{A}$?

The quantity of charge through a conductor is modeled as $Q = 4.00 \frac{\text{C}}{\text{s}^{4}} t^{4} - 1.00 \frac{\text{C}}{\text{s}} t + 6.00 \text{mC}$.

What is the current at time $t = 3.00 \text{s}$?

The charge on a capacitor in a circuit is modeled as $Q \left(t\right) = Q_{\text{max}} \text{cos} \left(\omega t + \phi\right)$. What is the current through the circuit as a function of time?