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Electricity electric circuits & electric current
Electric current and Resistors & Ohm’s Law voltage
Resistors in Series and Parallel Circuits & Electric Potential Difference
chapter 11 Work, Energy and Power
Formula calculation
100
What is the difference between primary cells and secondary cells.
Primary cells are not rechargeable because the chemical reaction are not reversible, secondary cells can be recharged.
100
What is the difference between conventional current and electron flow.
Conventional current flow from positive to negative. Electron flow from negative to positive.
100
___________ can measure the change in electric potential energy per coulomb of charge and ________ is defined as one joule per coulomb.
Voltage, Volt
100
The definition of energy and work.
the ability to do work，the measure of the amount of energy transformed from one form into another form of energy。
100
The unit for measuring energy usage.
Kilowatt-hour(kW-h)
200
What is the difference between a battery and a cell
A battery is the combination of two or more electric cells.
200
What is AC and DC? How are they differ?
DC is the electric current from an electric cell flows in a single direction. Alternating current happens when the electrons periodically reverse direction. In an AC circuit in North America, the current reverses its direction 60 times a second.
200
Cells in series or cells in parallel provide more charge in a given time and provide charge for longer time.
Parallel cells can provide more charge in a given time (greater current) and provide a given charge for a longer time (longer battery life).
200
A car rolling down a hill is an example of____________energy.
kinetic energy
200
Amount of time it takes to do 600 Joules of work using 5 Watts of power?
120 seconds
300
In a circuit, which line represents the positive side of the battery?
The longer line
300
What is a resistor and what is it measured in. Give two example of the type of material that makes up the resistor?
A RESISTOR is a component of an electrical circuit that resists, or opposes, the flow of electrical current. The resistor is the load in a circuit and converts electrical energy to another form of energy, such as light energy or heat energy. The unit of measurement for resistance is the OHM Ω. resistors are made of CARBON, METALWIRE wrapped around ceramic or plastic tubing
300
How should a voltmeter be connected to a battery to measure the voltage of the battery? Draw a circuit diagram to explain your answer.
The voltmeter can be connected to the energy source or it can be connected to the load.When you connect a voltmeter to the positive and negative terminals of a battery, the voltmeter measures the difference in volts between the positive and negative terminals
300
what happens to the kinetic energy when a ball rises?
It transforms into gravitational potential energy.
300
The time a 100 W light bulb takes to use 400 J of energy.
4 seconds.
400
Name three types of cells and where we're they used.
Lead-acid battery, for cars;alkaline cells, used in many electronic devices such as digital cameras and hand-held gaming system, also a type of primary cells;Nickel–cadmium cells and lithium ion cells are used in portable computers.
400
The starter motor of a car is connected to a 24 V battery. If the starter motor has 150 A of current going through it to start the car, what is the resistance of the starter motor?
R=V/I =12V / 150A =0.32 Ω The resistance of the starter motor is 0.32 Ω
400
What is the voltage of three 1.5 V cells connected in parallel to form a battery? What is the general rule for the voltage of a battery made from cells connected in parallel?
parallel Vt= V1=V2=V3 When electric cells are connected in parallel, they do not provide more voltage.
400
Energy that can be stored in an object, and give three examples.
Potential energy(PE). gravitational potential energy, elastic potential energy and chemical potential energy.
400
How much energy is used by a light bulb drawing 1.5 A on a standard 136 V circuit in 10 minutes?
122400 J.
500
Explain the current in parallel circuit
When devices are connected in a parallel circuit, the current splits up and some of the current goes through each device
500
1. A 92 Ω resistor has a current of 78 mA flowing through it. What is the voltage in the resistor? 2. A flashlight has a filament with a resistance of 10.7 Ω. The batteries provide 2.8 V. What is the current through the filament?
1. 78 mA ? 0.078 A V = IR = (0.078 A)(92 Ω) =7.2V 2. I= V/R = 2.8V / 10.7 Ω = 0.26 A
500
Three identical resistors are connected in parallel to an electric cell (Figure 8). In the third resistor (R3) the resistance is 63 Ω and the current is 23 mA. 1. What is the voltage (VT ) of the electric cell? 2. What is the total resistance (RT ) of the parallel group of resistors?
1. 23 mA ?= 0.023 A V3 = IR ? = (0.023 A)(63 Ω) =1.449 V 2. RT= R/n = 63/3Ω = 21 Ω
500
Energy can be converted from one type into another type of energy, and the total amount of energy remains constant.
the Law of Conservation of Energy.
500
On March 1, the energy reading on a home's energy meter is recorded at 56 270 kW-h. One month later, the same meter reads 56 825 kW-h. At a price of $0.07/kW-h, how much did the electricity for the month cost?
The electricity cost $38.85