Electric Circuits: Extra Problems
The problems below are provided as additional problems to
the original set of 34 Electric Circuits problems. Just like problems in the original set, these problems consist of a problem, an answer (revealed by clicking a link), an audio guided solution, and links to an
Overview page of formulas and to The Physics Classroom Tutorial pages. The Extra Problems pertain to the mathematics associated with electric potential, current, resistance, resistivity, power, and energy.
Problem Set A
Problem 1:
The compressor on an air conditioner draws 86.6 A when it starts up. If the start-up time is about 0.624 s, how much charge (in Coulombs) passes a cross-sectional area of the circuit in this time?
Problem 2:
It is observed that 2.24 Coulombs of charge flow through a light-bulb over the course of 3.1 minutes. There are three light bulbs in the circuit, lined up one after the other. Determine the amount of charge (in Coulombs) flowing through the third light bulb over the course of 6.4 minutes.
Problem 3:
If Avogadro's number of electrons pass by a given cross-sectional area in 25.5 minutes, find the current (in amps) in the conductor.
Problem 4:
If 6.13 x 1020 electrons flow past a given cross section of the wire in 14.9 minutes, what is the current (in milliAmps) in the wire?
Problem 5:
A person notices a mild shock if the current along a path through the thumb and index finger exceeds 80.5 microAmps. Determine the maximum allowable voltage (in volts) without shock across the thumb and index finger with a dry-skin resistance of 5.22 x 105 ohm.
Problem 6:
A person notices a mild shock if the current along a path through the thumb and index finger exceeds 80.5 microAmps. Determine the maximum allowable voltage (in micro-volts) without shock across the thumb and index finger with a wet skin resistance of 2022 milli-ohm.
Problem 7:
If a current of 80.2 mA exists in a metal wire, what quantity of charge (in Coulombs) flows past a given cross section of the wire in 28.3 minutes?
Problem 8:
A typical color television draws about 2.74 Amps when connected to a 120-Volt source. What is the effective resistance (in ohms) of the TV set?
Problem 9:
When operating at 120 volts, a resistor carries a current of 5.75 A. What current (in Amps) would be carried if the operation voltage is lowered to 87 V?
Problem 10:
Use resistivity values from the textbook to calculate the resistance (in milliOhms) of a piece of nichrome wire 240 cm long with a cross-sectional area of 0.0218 cm2.
Problem 11:
The heating element of a toaster is made of nichrome wire 1.08 mm in diameter. If the toaster has a resistance of 8.25 ohms, how long (in meters) is the wire? Use resistivity values from the textbook.
Problem 12:
A 214.44-cm piece of iron wire carries a current of 0.251 A when connected to a 6-V Battery. What length (in centimeters) of gold wire would carry the same current when connected to the battery if the gold wire has the same radius as the iron? Use resistivity values from the textbook.
Problem 13:
A toaster is rated at 620 Watts when connected to a 120-V source. What is the resistance (in ohms) of the toaster?
Problem 14:
How much current (in Amps) is being supplied by a 242-V generator delivering 129 kW of power?
Problem 15:
The sticker on a compact disc player says that it draws 318 mA of current at 9 V. What power (in Watts) does it dissipate?
Problem 16:
The tungsten heating element in a 2263-W heater is 4.88 m long, and the resistor is to be connected to a 120-V source. What is the cross-sectional area of the wire (in mm^2)? Enter your answer accurate to the fifth decimal place.
Problem 17:
What is the required resistance (in ohms) of an immersion heater that will increase the temperature of 1.66 kg of water from 1 degrees Celcius to 50 degrees Celcius in 15.4 min while operating at 120 V? Use 4.186 J/g deg as the specific heat of water.
Problem 18:
How much does it cost (in cents) to watch a complete 23.3 hour-long World Series on a 91.5 -W black-and white television set? Assume electricity costs 9.7 cents per kW•h.
Problem 19:
If electricity costs 9.70 cents per kW•h, estimate how much it costs a person (in cents) to dry his hair with a 1796 W blow dryer during a year's time? Assume that on average a person uses the hair dryer for 6.29 minutes a day all 365 days of the year.
Problem 20:
An advertisement for a vaporizer that operates on 110. V states that it converts 451 mL of water to steam in 62.8 minutes. Ignoring heat losses, determine the resistance (in ohms) of the vaporizer. The heat of vaporization of water is 2.26 x 10^6 J/kg and the density of water is 1.00 g/mL.