Physics Chapters 34 and 35

What;s the relationship among the units of measure for the 3 quantities related by Ohm's Law

1 ampere= 1 volt/ohm

Express the mathematical formula for electric power expressed in units

1 watt= 1 ampere times 1 volt

One kilowatt hour is the amount of energy consumed in ___ hour at the rate of ______ watts

1, 1000

Explain what would happen if a Van de Graff generator charged to a high potential was connected to a ground wire.

A surge of charge would flow through the wire. The flow would be brief because the sphere of the generator would quickly reach a common potential with the ground.

Why do current carrying wires become hot

Conduction electrons are accelerated by the electric field. before the electrons can gain appreciable speed, they bump into the anchored metallic ions in their paths and transfer some of their kinetic energy to them. This causes them to become hot.

If the power and voltage on a light bulb read 60 W, 120 V, how much current will flow through the bulb?

I=P/V I=60 W/120 V I= 0.5A

Why is it dangerous to handle electrical devices while taking a bath

If you are standing barefoot in a wet bathtub connected through its plumbing to the ground, the resistance between you and the ground is very small. Your overall resistance is lowered so much that the 120 volt potential difference may produce a harmful current through your body

How do batteries and generators supply electrical energy?

In a battery, chemical reactions occurring inside release electrical energy. In a generator, mechanical energy is converted to electrical energy.

State Ohm's Law

The current in a circuit is directly proportional to the voltage impressed across the circuit, and is inversely proportional to the resistance of the circuit.

Describe how the positive and negative terminals of a battery are indicated on a schematic diagram

The positive terminal is represented with a long line and the negative terminal with a short line.

Explain how the sustained flow of charge is analogous to the flow of water from a higher reservoir to a lower one.

Water will flow in a pipe that connects the reservoirs only as long as a difference in water level exists. The flow of water in the pipe, like the flow of charge in the wire that connects the Van de Graff generator to the ground, will cease when the pressures at the two ends are equal. For the flow to be sustained, there must be a suitable pump of some sort to maintain a difference in water levels. Then there will be a continual difference in water pressures and a continual flow of water. The same is true of electrical current.

What is a schematic diagram

a diagram that describes an electric circuit, using special symbols to represent certain circuit elements

Which is true: a. The resistance of a wire depends on the conductivity of the material used in the wire. b. the resistance of the wire does not depend on the thickness of the wire. c. longer wires have less resistance than shorter wires d. electric resistance depends on the temperature of the wire.

a, d

Suppose you have a completed circuit with three lamps connected in series. Circle the letter of the statement that correctly describes what happens if the filament of the middle lamp bums out. a. Current ceases, and the remaining two lamps will also go out. b. Both of the remaining lamps will stay lit. c. Only one of the remaining lamps will stay lit. d. The amount of current flowing through the circuit drops by one third.

a.

Which are true: a. energy is transported through connecting wires of a circuit at nearly the speed of light b. the electrons that make up an electric current travel at the speed of light c. the electric field inside a current carrying wire has no effect on the motion of conduction electrons. d. the random thermal motion of the electrons inside a wire is what produces current.

a.

SI unit used to measure electric current and is equivalent to 1 coulomb of charge per second

ampere

Circle the letter of each statement that is true about a completed electric circuit consisting of a battery, a lightbulb, and two wires. a. Electrons flow from the positive terminal of the battery to the negative terminal. b. The battery acts like a pump, causing current to flow through the circuit. c. The conduction electrons tend to pile up inside the bulb. d. The conduction electrons that drift through the circuit originate from the wires and the bulb filament

b,d

A complete path along which charge can flow

circuit

The source of electrons in the circuit is the

conducting circuit material itself

particles within a solid conductor that carry charge through a circuit

conduction electrons

electric power=

current times voltage

express Ohm's Law mathematically

current= voltage/resistance

The damaging effects of electric shock are the result of ______ passing through the body

currents

In current carrying wires, collisions interrupt the motion of the electrons so that their actual _______, or net speed through the wire due to the field, is extremely low.

drift speed

The flow of electric charge

electric current

What are resistors

elements in a circuit that are used to regulate current

True or false? the amount of charge that flows in a circuit doesn't depend on the voltage provided by the voltage source

false

true or false? The resistance of your body is much greater when you're soaked with water than when your skin is dry

false

The equivalent resistance of two resistors in parallel is __________________

half the value of either resistor

When you turn on an electrical lamp, what two forms of energy are produced?

heat and light

Describe the main disadvantage of a series circuit

if one device fails in a series circuit, current in the whole circuit ceases and none of the devices will work.

Electric resistance is measured in units called

ohms

Switch Position Effect open closed Which one of these a. cuts off electron flow b. allows electron flow

open -a closed -b

When connected in ______, devices in a circuit form branches, each of which is a separate path for the flow of electrons.

parallel

Charge flows when there is a __________ between the ends of a conductor.

potential difference

The relationship among current, voltage, and ______ is called Ohm's Law

resistance

The voltage drop across each device in a series circuit depends directly on its _______

resistance

Circuit Element resistance connecting wire battery open switch Symbol a. zigzag line b. broken line with one end tilted up at an, angle c. set of short and long parallel lines d. solid straight line

resistance- a connecting wire- d battery- c open switch- d

When connected in ______, devices form a single pathway for electron flow

series

What's a voltage source?

something that provides a potential difference

The total resistance to current in a series circuit is the ___ of the individual resistances along the circuit path

sum

The equivalent resistance of resistors in series is the ___________________

sum of their values

The resistance of some materials becomes zero at very low temperatures, this is known as

superconductivity

A gap in a circuit is usually provided by an electric _____

switch

Electric Power

the rate at which electrical energy is converted into another form such as mechanical energy, heat, or light

What's electric resistance

the resistance that a conductor offers to the flow of charge

what's the purpose of the third prong on a three prong electrical plug

the third prong is connected to the ground to prevent electric shock

Define equivalent resistance

the value of the single resistor that would comprise the same load to the battery or power source as a combination of resistors

Charges flow _____ a circuit because of an applied voltage ______ the circuit.

through, across

What is the purpose of connecting a fuse or circuit breaker in series along the supply line?

to prevent overloading in circuits

Is the following sentence true or false? The more devices you connect in parallel to your household supply line, the more you increase the total line current

true

True or false? The potential energy per coulomb of charge available to electrons moving between the terminals of a battery or generator is the voltage

true

true or false? a bird perched on a high voltage wire isn't shocked because there isn't a potential difference one part of its body and another

true

true or false? a pulsating electric field can travel through a circuit at nearly the speed of light

true

the net charge in a current-carrying wire

zero