Physics Electric Fields

What force would be exerted on an electron in an electric field with a magnitude of 9.9x10^7 N/C?

1.6x10^-11N

A battery with a voltage of 9.0 V is connected to a lamp. The current flowing in the circuit is 0.30 amps. The resistance of the lamp is ___

30Ω

Name a device that employs the special qualities of a photoresistor. How does this device work?

A circuit that includes a photoresistor is used in a light meter. The electronic circuit detects the potential difference and converts it to a measurement of illuminance

a device used to measure the current in part of a circuit

Ammeter

the value of a single resistor that could replace all resistors in a circuit without changing the current

Equivalent resistance

Negative charge flows from a higher potential to a lower potential.

False, positive

a device that detects small differences in current caused by an extra current path and opens the circuit

Ground-fault interrupter

What is a Van de Graaf generator? How can one be used to show field lines?

It transfers large amounts of charge from one part of the machine to the top. If someone touches it, it is charged electrically. The charges on the person's hair repel one another and follow the field lines.

How do you find the potential drop across an individual resistor?

Multiply the current in the circuit by resistance

What is the purpose of a voltage divider?

Produces a voltage source of magnitude from a higher voltage battery

What determines the resistance of a photoresistor?

The amount of light that strikes it

Why must the net change in potential be zero as current moves through a circuit?

The circuit electric energy source raises the potential by an amount equal to the potential drop

a device used to measure the potential drop across some part of a circuit

Voltmeter

If a 200Ω resistor is connected to a 5V battery, the current in the circuit will be ___.

a.) 0.025A b.) 2.5A c.) 40A d.) 1000A

If a 9.0V battery delivers 0.5A of current to a heater, the power consumed by the heater is

a.) 0.056W b.) 4.5 W c.) 9.0W d.) 18W

If a light bulb is rated at 50W, the amount of energy consumed in 30 minutes is

a.) 2kWh b.) 30kWh c.) 30J d.) 90,000J

A 60W lightbulb illuminated day and night for 30 days consumers ___ of energy.

a.) 43.2J b.) 43.2 kWh c.) 1800 kWh d.) 1.5x10^12 J

If a family's electric bill is $74.00 per month and the cost of electricity is $0.12 per kWh, how much electricity does the family use per month?

a.) 8.9 kWh b.) 270 kWh c.) 620 kWh d.) 620x10^2 kWh

What equation defines the electric potential difference?

a.) E=F/q b.) q= mg/E c.) v= J/C d.) ▵V= W/q

Which of the following equations is not correct?

a.) I=▵Vsource/(R1+R2) b.) I=▵Vsource/R c.) I=▵Vsource/(R1+R2+R3) d.) R3+(▵Vsource/(R1+R2)

the formula for power loss in a wire is

a.) P=IR^2 b.) P=IR c.) P=I^2R d.) P=RV

Which of the following equations computes the equivalent resistance for a series circuit with four resistors?

a.) R= R1 + R2 + R3 + R4 b.) R= R1 x R2 x R3 x R4 c.) 1/R= 1/R1 + 1/R2 + 1/R3 1/ R4 d.) R=(R1 x R2) / (R3 x R4)

A positive test charge is located at Point A. If the test charged is moved to a Point B and then back to Point A, what is the change in electric potential?

a.) The electric potential becomes zero b.) The electric potential decreases c.) The electric potential does not change d.) The electric potential increases

Only ___ electrical potential can be measured

a.) absolute values of b.) attractions between c.) differences in d.) points of

The electric potential ___ when a positive charge is moved toward a negative charge

a.) becomes positive b.) decreases c.) increases d.) stays the same

The kilowatt-hour is a unit of ___

a.) current b.) energy c.) potential d.) power

For a wire that obeys Ohm's law, the resistance of a wire depends on the __ the wire.

a.) current in b.) length of c.) power delivered by d.) voltage across

The purpose of increasing the voltage when transmitting electric power over long distances is to __.

a.) decrease joule heating loss b.) decrease resistance of wires c.) increase current in wire d.) increase kilowatt-hours

In an electric circuit, the increase in voltage provided by the generator or other energy source, ▵Vsource is equal to the ___ of voltage drops across the resistors.

a.) difference b.) product c.) sum d.) average

When you do positive work on a two-charge system, the electric potential energy ___.

a.) disappears b.) decreases c.) does not change d.) increases

How would you calculate the total current of this circuit?

a.) find the average of the currents through each path b.) subtract the currents through each path c.) add the currents through each path d.) It is not possible to calculate total current for this circuit

The current is ___ a series circuit

a.) higher at the beginning of b.) the same everywhere in c.) lower at the beginning of d.) variable in

In the transmission of electric energy, some power is lost to thermal energy. Electrical engineers call this unwanted thermal energy the ___.

a.) joule heating loss b.) resistance c.) output voltage d.) long-distance line

In a series circuit, the equivalent resistance is __ any single resistance

a.) larger than b.) determined by c.) equal to d.) smaller than

How many current paths are in this circuit

a.) one b.) three c.) four d.) five

A device that can be used to change the current in a circuit in a continuous way is a ___

a.) potentiometer b.) battery c.) motor d.) lamp

What type of circuit does the diagram represent

a.) series circuit b.) parallel circuit c.) a combination series parallel circuit d.) a tandem circuit

If the battery voltage does not change, adding more devices in series _____ the current

a.) sometimes decreases b.) always decreases c.) sometimes increases d.) always increases

If the 10Ω resistor were removed from the circuit, which of the following would not be true?

a.) the current through the 20Ω resistor would be unchanged b.) the sum of the current in the branches of the circuit would change c.) the total current through the generator would change d.) the current through the 50Ω resistor would change

To find the current through a series circuit, first calculate the ___.

a.) voltage b.) equivalent resistance c.) power d.) equivalent voltage

A ___ is the unit of a current

ampere

Current is measured in units called

amperes

A(n) ______ is a wire coil in an electric motor made of many loops mounted on a shaft or axle.

armature

The force on a current-carrying wire in a magnetic field is ____ both the direction of the magnetic field and the direction of current.

at right angles to

A ___ converts chemical energy into electrical energy

battery

the ration of an object's stored charge to its potential difference, measured in farads

capacitance

a device with a specific capacitance that is used in electrical circuits to store charge

capacitor

an automatic switch that opens a circuit when the current reaches some set value

circuit breaker

a circuit that has some branches in parallel and some in series

combination series-parallel circuit

A ___ is the flow of positive charge

conventional current

The magnitude of the torque acting on the loop is proportional to the magnitude of the ____.

current

The ____ of the force on the wire resulting from the magnetic field can be determined by using the third right-hand rule.

direction

A group of neighboring atoms whose electrons' magnetic fields all align in the same direction is called a(n) ______.

domain

One side of the loop is forced ____; the other side is forced up.

down

A ___ is a closed loop in which electrons can move

electric circuit

The ___ is the flow of charged particles

electric current

the vector quantity that relates the force exerted on a charge to the size of the charge

electric field

the lines providing a picture of the size and strength of the field around a charged object

electric field lines

Do the field lines and electric fields actually exist? How are field lines and electric fields useful?

electric fields do, but field lines do not. Field lines provide a model of an electric field and electric fields provide a method of calculating the force on a charged body

A(n) ______ is a device that converts electric energy into totational kinetic energy.

electric motor

the work done moving a positive test charge between two points in an electric field divided by the magnitude of the test charge

electric potential difference

A magnet created when a current flows through a coil of wire is a(n) ______.

electromagnet

the potential difference of zero between two or more positions in an electric field

equipotential

A loudspeaker changes electrical energy directly into sound energy.

false

The ______ can be used to determine the direction of a magnetic field relative to the direction of a conventional current.

first right-hand rule

a short piece of metal that melts if a current that is too large passes through it

fuse

A(n) ______ is a device used to measure very small currents.

galvanometer

This principle is used in ____ to measure small currents.

galvanometers

designed to convert electric energy to thermal energy

heater

A ___ is a unit of energy

kilowatt-hour

The current passing through the ____ goes in one end and out the other.

loop

______ exist in a region of space where a magnetic force occurs.

magnetic field

____ that exert forces on a loop of wire carrying a current can be used to measure very small currents.

magnetic fields

The number of magnetic field lines that pass through a surface is called ______.

magnetic flux

converts electric energy to kinetic energy

motor

A galvanometer can be converted to an ammeter by connecting it in ____ with a resistor that has a resistance smaller than that of the galvanometer.

parallel

a circuit in which there are several different paths for a current

parallel circuit

In a ___ there is more than one path for the current

parallel connection

A magnet is ______, which means that it has two distinct and opposite ends.

polarized

___ measures the rate at which energy is transferred. The formula for the power is ___. The energy carried by an electric current depends on the ___ transferred and the ___ difference the charge undergoes. The formula for the amount of energy transferred is ___. The rate of flow of the charge is called the electric ___. The formula for the rate of flow of charge is___. Another formula for the power delivered by an electric current is___.

power, P=Vi, charge, potential, E=Pt, current, I=V/R, P+ V^2/R

A small spring in a galvanometer exerts a torque that opposes the torque resulting from the current. Thus the amount of torque is ____ to the current.

proportional

The ___ of a wire determines how much current will flow through the wire when a voltage is applied

resistance

A ____ is a device designed to have a specific resistance

resistor

The ______ can be used to determine the direction of a field produced by an electromagnet relative to the flow of a conventional current.

second right-hand rule

To convert a galvanometer is connected in ____ with resistor called a ____.

series multiplier

What type of circuit is used as a voltage divider?

series circuit

a circuit in which all current travels through each device

series circuit

In an ___ there is only one path for the current

series connection

the occurrence when a circuit forms that has a very low resistance

short circuit

A long coil of wire that contains many loops is called a(n) ______.

solenoid

The direction of Earth's magnetic field is toward the ____.

south magnetic pole

A ___ is a material with zero resistance

superconductor

The strength of a magnetic field is measured in ____.

teslas

The magnitude of the force on a current-carrying wire in a magnetic field is proportional to ____.

the strength of the field, the current of the wire, and the length of the wire in the magnetic field

The ______ can be used to determine the direction of the force on a current-carrying wire in a magnetic field.

third right-hand rule

The resulting ____ rotates the loop.

torque

The amplifier that drives a loudspeaker sends a current through a coil of wire mounted on a paper cone.

true

The flow of electrons is called conventional current

true

The force exerted on the coil of wire in a magnetic field in a loudspeaker pushes the coil into or out of the field, depending on the magnitude of the current.

true

The force on a current-carrying wire in a magnetic field is used in a loudspeaker.

true

The motion of the coil in a loudspeaker causes the cone to vibrate, which creates sound waves.

true

How can you find the electric field from two charges?

use the vector sum of the 2 charges

1 J/C

volt

A series circuit used to produce a voltage source from a higher voltage battery

voltage divider

A galvanometer can be used a(n) ____ or an ammeter.

voltmeter

Power is measured in units called

watts

A small loop of ____ that is carrying a current is place in the strong magnetic field of a permanent magnet.

wire