# Day 114 (problems)

### Try the following problems:

How many electrons per second pass through a section of wire carrying a current of 0.7 A?

Answer (4.4 x 10^18 electrons/s)

An electron gun in a TV set shoots out a beam of electrons. The beam current is 1.0 x 10-5 A. How many electrons strike the TV screen each second? How much charge strikes the screen in a minute?

Answer (6.3 x 10^13 electrons/s, -6 x 10^-13 C/min)

Determine the potential difference between the ends of a wire of resistance 5.0 Ω if 720 C passes through it per minute.

Answer (60 V)

What potential difference is required to pass 3.0 A through 28 Ω?

Answer (84 V)

What is the current through an 8.0 Ω toaster when it is operating on 120 V?

Answer (15 A)

An ammeter is connected in series with an unknown resistance, and a voltmeter is connected across the terminals of the resistance. If the ammeter reads 1.2 A and the voltmeter reads 18 V, compute the value of the resistance. Assume ideal meters.

Answer (15 Ω)

A copper bus bar carrying 1200 A has a potential drop of 1.2 mV along 24 cm of its length. What is the resistance per meter of the bar?

Answer (4.2 uΩ/m)

The resistivity of a silver wire is 1.59 x 10-8 Ωm. The radius of the wire is 5.04 x 10-4 m. If the length of the wire is 3.00 m, what is the resistance of the wire?

Answer (.0598 Ω)

A 4 A current is maintained in a simple circuit with a total resistance of 2Ω . How much energy is dissipated in 3 seconds?

Answer (96 J)

A 40 W light bulb and a 60 W light bulb are designed for use with the same voltage. What is the ratio of the resistance of the 60 W bulb to the resistance of the 40 W bulb?

Answer (0.67)

A 5A current is maintained in a simple circuit that consists of a resistor between the terminals of an ideal battery. If the battery supplies energy at a rate of 20 W, how large is the resistance?

Answer (0.8 Ω)

A computer monitor uses 2.0 A of current when it is plugged into a 120 V outlet. The monitor is never turned off. What is the yearly cost of operating the monitor if the cost of electricity is \$0.12/kWh?

Answer (\$250)

A resistor dissipates 1.5W when it is connected to a battery with a potential difference of 12V. What is the resistance of the resistor?

Answer (96 Ω)

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