Which change to a circuit is most likely to increase its electrical power? A. Increase its current and increase its voltage. B. Decrease its current and increase its voltage. C. Decrease its current and decrease its voltage. D. Increase its current and decrease its voltage.

Construct Your Own Problem Consider a person working in an environment where electric currents might pass through her body. Construct a problem in which you calculate the resistance of insulation needed to protect the person from harm. Among the things to be considered are the voltage to which the person might be exposed, likely body resistance (dry, wet, ...), and acceptable currents (safe but sensed, safe and unfelt, ...).

The following statements are related to household circuits and electrical safety. Determine whether each statement is true (T) or false (F). (a) Circuit breakers are wired in series with the outlets they protect. (b) A circuit breaker rated at 20 A provides a constant current of 20 A to each outlet in the circuit. (c) Three-wire electrical cords help prevent dangerous electrical shocks by grounding the case of a device.

Some makes of older cars have 6.00-V electrical systems. (a) What is the hot resistance of a 30.0-W headlight in such a car? (b) What current flows through it?

An electric circuit that is not a complete path is called a(n) ___ circuit. (8.2)

Integrated Concepts A battery-operated car utilizes a 12.0 V system. Find the charge the batteries must be able to move in order to accelerate the 750 kg car from rest to 25.0 m/s. make it climb a 2.00 102 m high hill, and then cause it to travel at a constant 25.0 m/s by exerting a 5.00 102 N force for an hour.

Construct Your Own Problem Consider a battery used to supply energy to a cellular phone. Construct a problem in which you determine the energy that must be supplied by the battery, and then calculate the amount of charge it must be able to move in order to supply this energy. Among the things to be considered are the energy needs and battery voltage. You may need to look ahead to interpret manufacturer’s battery ratings in ampere hours as energy in joules.

You have been called in as an expert witness in a civil case. The case involves a dispute between neighbors. The plaintiff neighbor is complaining about a buzzing noise during the night that prevents the plaintiff from sleeping. He claims that the buzzing is coming from a light fixture on the defendants porch ceiling. The defendant likes to do installations and repairs himself and has done a sloppy job of installing the light fixture. The fixture hangs vertically from a single wire that is attached through the porch ceiling and down the wall to one connector in a nearby electrical outlet. The second wire is hung horizontally with strings at the level of the light and then runs down the wall to the other connector in the outlet. The defendant leaves the light on all night long for security. Recalling his high school physics, the plaintiff states that the combination of the 60-Hz household voltage and the magnetic field of the Earth results in an oscillating driving force on the single wire from which the light fixture hangs vertically. This, in turn, sets up a standing wave in the wire, and that is the cause of the buzz. You have been hired by the defense attorney. Upon hearing the details of the case, you obtain permission from the defendant and make measurements. The mass of the light fixture is 17.5 kg. The vertical wire from which it hangs is 0.150 m long and has a mass of 0.030 kg. Is the plaintiff correct that the magnetic field of the Earth is causing the buzzing of the wire? Ignore any effect of the second wire.

Body injury from electricity depends on the magnitude of the current and its path (see the 8.2 Highlight: Electrical Effects on Humans, section 8.3). However, signs warning Danger. High Voltage are commonly seen ( Fig. 8.35). Shouldnt the signs refer to high current? Explain. Figure 8.35 High Voltage or High Current?

A 0.0200- ammeter is placed in series with a 10.00- resistor in a circuit, (a) Draw a circuit diagram of the connection, (b) Calculate the resistance of the combination, (c) If the voltage is kept the same across the combination as it was through the 10.00- resistor alone, what is the percent decrease in current? (d) If the current is kept the same through the combination as it was through the 10.00-resistor alone, what is the percent increase in voltage? (e) Are the changes found in parts (c) and (d) significant? Discuss.