Energy/power/work
38 A hair dryer with a resistance of 9.6 ohms operates at 120 volts for 2.5 minutes. The total electrical energy used by the dryer during this time interval is
(1) 2.9 × 10^3 J
(2) 3.8 × 10^3 J
(3) 1.7 × 10^5 J
(4) 2.3 × 10^5 J
(4) 2.3 × 10^5 J
A lightbulb with a resistance of 2.9 ohms is operated using a 1.5-volt battery. How many amperes would an ammeter read through the circuit?
0.52 A
If several resistors are connected in series in an electric circuit, the potential difference across each resistor
(1) varies directly with its resistance
(2) varies inversely with its resistance
(3) varies inversely with the square of its resistance
(4) is independent of its resistance
(1) varies directly with its resistance
17 Compared to the resistivity of a 0.4-meter length of 1-millimeter-diameter copper wire at 0°C, the resistivity of a 0.8-meter length of 1-millimeter-diameter copper wire at 0°C is
(1) one-fourth as great
(2) one-half as great
(3) the same
(4) four times greater
(3) the same
16 Which forces can be either attractive or repulsive? (1) gravitational and magnetic
(2) electrostatic and gravitational
(3) magnetic and electrostatic
(4) gravitational, magnetic, and electrostatic
(3) magnetic and electrostatic
16 How much work is required to move an electron through a potential difference of 3.00 volts?
(1) 5.33 × 10^–20 J
(2) 4.80 × 10^–19 J
(3) 3.00 J
(4) 1.88 × 10^19 J
(2) 4.80 × 10^–19 J
13 A radio operating at 3.0 volts and a constant temperature draws a current of 1.8 × 10−4 ampere. What is the resistance of the radio circuit?
(1) 1.7 × 10^4 Ω
(2) 3.0 × 10^1 Ω
(3) 5.4 × 10^−4 Ω
(4) 6.0 × 10^−5 Ω
(1) 1.7 × 10^4 Ω
50 A combination of two identical resistors connected in series has an equivalent resistance of 10. ohms. What is the equivalent resistance of the combination of these same two resistors when connected in parallel?
(1) 2.5 Ω
(2) 5.0 Ω
(3) 10. Ω
(4) 20. Ω
(1) 2.5 Ω
18 A net charge of 5.0 coulombs passes a point on a conductor in 0.050 second. The average current is
(1) 8.0 × 10^−8 A
(2) 1.0 × 10^−2 A
(3) 2.5 × 10^−1 A
(4) 1.0 × 10^2 A
(4) 1.0 × 10^2 A
37 What is the magnitude of the electrostatic force exerted on an electron by another electron when they are 0.10 meter apart?
(1) 2.6 × 10^−36 N
(2) 2.3 × 10^−27 N
(3) 2.3 × 10^−26 N
(4) 1.4 × 10^−8 N
(3) 2.3 × 10^−26 N
32 A particle with a charge of 3.00 elementary charges moves through a potential difference of 4.50 volts. What is the change in electrical potential energy of the particle?
(1) 1.07 × 10^−19 eV
(2) 2.16 × 10^−18 eV
(3) 1.50 eV
(4) 13.5 eV
(4) 13.5 eV
DAILY DOUBLE (worth 600 pts), open to any team. Closest answer wins
In 1977, we launched Voyager 1. It reached Saturn by 1980, traveling about 1.2 billion km from Earth. After photographing Saturn and several of its Moons, it has continued its journey and passed into interstellar space. In 2026, approximately how far is it from Earth? Give your answer in billions of km.
25.4 billion km
A 20.-ohm resistor, R1, and a resistor of unknown resistance, R2, are connected in parallel to a 30.-volt source, as shown in the circuit diagram below. An ammeter in the circuit reads 2.0 amperes. Determine the equivalent resistance of the circuit.
15 Ω
45 A tungsten wire has resistance R at 20°C. A second tungsten wire at 20°C has twice the length and half the cross-sectional area of the first wire. In terms of R, the resistance of the second wire is
(1) R/2
(2) R
(3) 2R
(4) 4R
(4) 4R
An electric motor has a rating of 4.0 × 102 watts. How much time will it take for this motor to lift a 50.-kilogram mass a vertical distance of 8.0 meters? [Assume 100% efficiency.]
(1) 0.98 s
(2) 9.8 s
(3) 98 s
(4) 980 s
(2) 9.8 s