Phy Sci 6ed Chap 19 Review

Your stereo system uses 11.8 A of electricity on a 120 V system. If electricity costs $0.13/kW*h, how much will it cost to run the stero system continuously for a week?

• $11.25
• $30.93

• $25.89

• $47.42

Answer explanation

What we know: I =11.8 A, V = 120 V, electricity costs $0.13/kWh

unknowns: P, E, Cost

Find power: P = VI, P = (120)(11.8) = 1416 W

Find energy: P = E/t so E = Pt,

How many hours (t) in a week: 7(24) = 168 h

Convert Watts to Kilowatts: 1416 W = 1.416 kW

E - (1.416 W)(168 h) = 238 kW*h

Cost = 238($0.13) = $30.93

A series circuit has a two resistors, one with 8 Ω, the other with 4 Ω. If the current going through the circuit is 2.7 A, what is the voltage of the circuit's battery?

• 32 V

• 24 V

• 36 V

• 40 V

Answer explanation

Because the circuit is in series, the resistors can be totaled to 12 Ω that the current goes through, so

V = IR

V = (2.7 A)(12 Ω) = 32 V

A circuit has 3 resistors in parallel, R1 = 10 Ω, R2 = 20 Ω, R3 = 20 Ω. If the circuit is powered by a 20 V battery, how much current is passing through R1, and what is the voltage drop over R1?

• I = 2.0 A, V = 20 V

• I = 5.0 A, V = 6.7 V

• I = 0.5 A, V = 20 V

• I = 2.0 A, V = 10 V

Answer explanation

parallel circuits have the same voltage going through each path, so each resistor experiences the same voltage drop of 20 V, but the current splits, so the current going through R1 is

I1 = V/R1 = (20 V)/(10 Ω)

I = 2.0 A

Draw a series circuit consisting of a battery, a resistor, and a capacitor. then add a voltmeter in parallel with the resistor.

batteries, photovoltaic cells, hydrogen fuel cells all use

• DC power

• AC power

• neither

• both

electrical generators use

• AC power

• DC power

• both

• neither

Define a short circuit

• a circuit that is small enough not to have internal resistance in the wires

• a circuit that uses less than 1 kW of power

• a circuit that is only in series

• current that takes an unintended path

What makes something an electrical conductor?

• Presence of free electrons that can move easily within the material
• Presence of fixed protons within the material
• High resistance to electric current flow
• Absence of any atoms in the material

What is direct current?

• A current that changes direction constantly.
• the current that is directly out of a battery

• An electric current that flows in multiple directions.
• An electric current that flows in one direction consistently.

What is the primary difference between static and current electricity?

• current electricity is when charges are moving constantly, static has the charges stationary on the surface of objects

• the is no difference

• current electricity is capable of doing work while static electricity is not really useful for doing work