Suppose two charges, q and 3q, are placed 3.39 m
apart. If the magnitude of the electric force between the charges is
2.4 10 6 N, what is the value of q?
Suppose two charges, q and 3q, are placed 3.39 m
apart. If the magnitude of the electric force between the charges is
2.4 10 6 N, what is the value of q?
Consider a group of
4.00 103 protons and a group of 3.20 105 electrons that are 1.00 km
apart. Calculate the magnitude of the electric force between them.
Calculate the magnitude of the electric force if each group contains
3.20 105 particles and if the separation distance remains the same.
An electric field of 9.0 N/C is directed along the positive x-axis.What is
the electric force on a –6.0 C charge in this field?
Millikan’s experiment measures the charge of an electron by suspending
charged oil droplets in an electric field. If an oil droplet with a mass
of 3.35 10–15 kg has the same charge as an electron.What electric
force is required to balance the weight of the oil droplet?
An electric field of 4.0 103 N/C is directed downward. If the electric
force on a charge is 6.43 10–9 N, what is the charge?
After brushing your hair many times, you notice that your hair is attracted
to the brush. Suppose a charge of +64 nC is on the brush and a
charge of 64 nC is on your hair.What is the electrical potential energy
associated with your hair and the brush when you hold the brush
0.95 m from your hair?
A magician holds a charged wand over scattered confetti and the confetti
moves to the wand. Suppose the confetti has a charge of 55 nC
and the wand has a charge of 77 nC.When the electrical potential energy
associated with the wand and the confetti is 1.3 10–2 J, how far
is the wand from the confetti?
Suppose you would like to develop a hat that wouldn’t fall off someone’s
head by putting enough charge on the hat so that it would stay
no matter how much the wind blew. You begin by rubbing a silk hat
against your head so that the same amount of charge collects on the
hat as the charge on your head.When you wear the hat (r = 1.25 
10–3 m), the electrical potential energy associated with the hat and
your head is 1.25 10–4 J. The hat stays as you walk into the wind.
a. How much charge was on the hat?
b. How much charge was on your head?
c. Suppose your friend approaches and puts the hat on. Is the hat
likely to stay on your friend’s head by charge alone? Why or why
not?
How far from an electron is the electric potential 1.0 V?
Suppose a transmitter uses a 4550 pF parallel-plate capacitor in a vacuum.
Each plate has an area of 6.4 10–3 m2. The capacitor is placed
across a potential difference of 36 kV.What is the distance between the
plates?
Polyester capacitors can have a capacitance of 5.0 10–5 F.What potential
difference is required to store 6.0 10–4 C?
A total charge of 76 C passes through a cross-sectional area of a copper
wire in 19 s.What is the current in the wire?
The current through a light bulb in a flashlight is 0.750 A.
a. How much charge passed through the filament
• in 20.0 s?
• in 5.00 min?
• in 2.00 h?
The motor of a garbage disposal has a resistance
of about 25.0 Ω. If the current through the motor equals 4.66 A,
What is the potential difference across the motor’s terminals?
A washing machine motor carries a current through a circuit with a resistance
of 12.2 Ω. If the washing machine is plugged into a 120 V outlet,
what is the current in the motor?
If the potential difference across
the car’s motor is 720 V and the resistance was 0.30 Ω, how much
power was needed for the car to run?
A microwave oven requires 1750 W of power to cook food. If the oven
is plugged into a 120 V outlet, what is the resistance in the oven’s
circuit?
A bread machine requires 1200 W to bake bread. How much time is required
for it to use 1.512 1010 J of energy?
Suppose you receive an electric bill which states the following:
Final Meter Reading 24422 kW•h
Previous Meter Reading 24204 kW•h
Cost of Electricity Used for 20 Days $0.078/kW•h
How much must you pay the electric company?
The ten reactors of the nuclear power station in Fukushima, Japan, produce
8.8 109 W of electric power. If you have $1,000,000, how many hours
of the station’s energy output can you buy? Assume a price of $0.081/kW•h.
Draw a schematic
diagram of an electric circuit that contains one battery, two light bulbs,
two resistors, and two switches.
A 9- Ωresistor is connected in series with another resistor across a 9.0-V
battery. The current in the circuit is 0.33 A. Calculate the value of the
unknown resistance.
A portable lamp has three bulbs wired in series: one bulb has a resistance
of 96 Ω, one bulb has a resistance of 48 , and one bulb has a resistance
of 29 Ω. If the voltage across the lamp is 115 V, what is the current
through the lamp’s circuit?
A 10 Ωresistor, a 12 Ωresistor, a 15 Ωresistor and an 18 Ωresistor are
connected in parallel across a potential difference of 12 V. What is the
equivalent resistance?
Two bulbs are wired in parallel: one bulb has a resistance of 3.3 Ω, and
the other bulb has a resistance of 4.3 Ω. If the voltage across the circuit
is 1.5 V, what is the current through each bulb?