Chapter 7 Electricity
3 Ω
A 0.7 ohm, a 1.5 ohm, and a 0.8 ohm resistor are connected in series across a 90 V battery. What is the resistance of the entire circuit?
3 A
A 10 ohm, a 15 ohm, and a 5 ohm resistor are connected in series across a 90 V battery. What is the current of the entire circuit?
150 Ω
Find the resistance of an electric light bulb if there is a current of 0.8 A and a potential difference of 120 V.
6.3 A
What is the current through an electric heater with a resistance of 38 ohms when the potential difference is 240 V?
series circuit
current has only one loop to flow through
The meter reading for June was 84502 kWh, & on July the meter read 87498. If the cost of electricity was $0.12 per kWh . What was the electric bill for June ?
...$359.52
What is the voltage across a 2-ohm resistor if a current of 0.5 amperes flows through it?
1 volt
What is the current flow in a circuit with an applied voltage of 120 volts and a resistance of 80 ohms?
1.5 amperes
What is the current flowing through a 24-ohm resistor connected across 240 volts?
10 amperes
What is the voltage across a 10-ohm resistor if a current of 1 ampere flows through it?
10 volts
How many times a second does lightning strike the Earth?
100
What is the current flowing through a 100-ohm resistor connected across 200 volts?
2 amperes
What is the voltage across a 10-ohm resistor if a current of 2 amperes flows through it?
20 volts
What is the resistance of a circuit that draws 4 amperes from a 12-volt source?
3 ohms
What is the resistance of a circuit in which a current of 3 amperes flows through a resistor connected to 90 volts?
30 ohms
What is the resistance in a circuit for which the applied voltage is 12 volts and the current flow is 1.5 amperes?
8 ohms
30 A
A 0.7 ohm, a 1.5 ohm, and a 0.8 ohm resistor are connected in series across a 90 V battery. What is the current of the entire circuit?
30 Ω
A 10 ohm, a 15 ohm, and a 5 ohm resistor are connected in series across a 90 V battery. What is the resistance of the entire circuit?
96 V
A 120 ohm resistor has 0.8 A of current flowing through it. Calculate the voltage.
150 V
A 75 ohm resistor has 2A of current flowing through it. Calculate the voltage.
dry cell batteries
A cell consists of two electrodes surrounded by a material called an electrolyte
104.2 V
A circuit with 4 A flowing through it has a 26.05 ohm resistor attached to it. How much voltage much power the circuit?
120 W
A laptop draws 2 A of current when connected to a 120 volt circuit. Calculate its power.
60 Ω
A laptop draws 2 A of current when connected to a 120 volt circuit. Calculate its resistance.
conductor
A material in which electrons are able to move easily
circuit breaker
A reusable safety switch that breaks the circuit when the current becomes too high
60 W
An alarm clock draws 0.5 A of current when connected to a 120 volt circuit. Calculate its power.
240 Ω
An alarm clock draws 0.5 A of current when connected to a 120 volt circuit. Calculate its resistance.
Lead-acid batteries
Contains a series of six wet cells made up of lead and lead dioxide plates in a sulfuric acid solution
How much will it cost to run the TV if the cost of energy is $0.10 per kWh ?
Cost = kWh * Hours Cost=.55 * $0.10 * 1 hour Cost = $0.06
How much will it cost to run the TV if the cost of energy is $0.10 per kWh ?
Cost = kWh * Hours Cost=4.4 kWh * $0.10 * 1 hour Cost = $0.44
TV operates 5 amps on a 110 volt circuit for one hour. Calculate kWh
Determine Power: P=V * I P=110 volts*5 amps P=550 watts Convert watts to kW : 550 watts * (1kw / 1,000 watts) 0.55 kW Multiply by hours .55kW * 1 hour = .55 kWh
TV operates 5 amps on a 110 volt circuit for one hour. Calculate kWh
Determine Power: P=V * I P=110 volts*5 amps P=550 watts Convert watts to kW : 550 watts * (1kw / 1,000 watts) 0.55 kW Multiply by hours: 0.55 kW * 1 hour = 0.55 kWh
TV operates 20 amps on a 220 volt circuit for one hour. Calculate kWh
Determine Power: P=V * I P=220 volts*20 amps P=4400 watts Convert watts to kW : 4400 watts * (1kw / 1,000 watts) 4.4 kW Multiply by hours: 4.4 kW * 1 hour = 4.4 kWh
96 Ω
Find the resistance of an electric light bulb if there is a current of 1.25 A and a potential difference of 120 V.
6.3 W
How much power is used by a 9V remote control that has a current of 0.7A?
What formula is used to calculate current in a circuit?
I = V / R
108 W
If a 40 V blender is supplied with 2.7 A of current, how much power will the blender have?
14.8 Ω
If a 40 V blender is supplied with 2.7 A of current, what amount of resistance will the blender have?
108 V
If a blender that has 40 ohms of resistance is supplied with 2.7 A of current, what amount of voltage will be used by the blender?
Electrons
Negatively charged particles
Protons
Positively charged particles
What formula is used to calculate resistance in a circuit?
R = V / I
True or False - All atoms are held together by electric forces between protons and electrons that are much larger than the gravitational forces between the atoms.
True
What formula is used to calculate voltage in a circuit?
V = I x R
E = electrical energy (kilowatt hour) kWh P = electric power (kilowatt) kW t = time (hours) h
What do letters in the electric energy equation represent?
150 W
What is the power of a 125 V appliance with 1.2 A flowing through it?
104.2 Ω
What is the resistance of a 125 V appliance with 1.2 A flowing through it?
6.3 V
What is the voltage needed to power a 1.26 A RC car with a resistance of 5 ohms?
What is lightning?
a large discharge of static electricity
insulator
a material that doesn't allow electrons to move through it easily
As the amount of charge on either object increases, the electrical force __________
also increases
law of conservation of charge
charge can be transferred from object to object but cant be created or destroyed
wet cell batteries
contains two connected plates made of different metals or metallic compounds in a conducting solution
parallel circuit
contains two or more branches for current to flow through
ohm's law
current in a circuit equals the voltage difference divided by the resistance.
The force between electric charges depends on
distance between charge; the force decreases as the charges get farther away
Which has less resistance, electrical conductors or insulators?
electrical conductors
Fuses
has a thin strip of metal that will melt if to much current flows through. -needs to be replaced once overloaded. -protects circuits from overheating.
The resistance of a conductor __________ as the conductor becomes longer and thinner.
increases
How is the electric resistance of materials related to the increase in temperature?
it increases as the temperature increases
What are ways to provide grounding?
lightning rods, plumbing fixtures
What are the best conductors?
metals
What are some good insulators?
plastics, wood, rubber, glass
Grounding
providing a path for electric charges to flow safely into the ground
voltage difference
push that causes charges to move and is measured in volts
electrical power
rate at which electrical energy is converted to another form of energy
charging by induction
rearrangement of electrons on a neutral object caused by a nearby change in induction
An electric field
surrounds every electric charge and exerts the force that causes other electric charges to be attracted or repelled
resistance
tendency for a material to oppose the flow of electrons changing the electrical energy into thermal energy and light
static electricity
the accumulation of excess electric charges on an object
What causes thunder?
the expansion and contraction of the air heated by lightning
charging by contact
the process of transferring charge by touching or rubbing
kilowatt-hour
unit of electrical energy
P = electric power (watts) W I = current (amperes) A V = voltage difference (volts) V
What do the letters in the electric power equation represent?
circuit
closed conducting path
An atom is electrically neutral because
the numbers of protons and electrons are equal
