Section 3.1
Section 3.2
Section 3.3
Section 3.4
Random
100
Which of the following is an example of mechanical energy?
a) plugging in an iphone
b) lighting a fire
c) digesting an apple
d) running up a hill
d) running up a hill
100
Which of the following statements is TRUE:
a) Like poles ATTRACT.
b) Unlike poles REPEL.
c) Unlike poles ATTRACT and like poles REPEL.
d) Unlike poles REPEL and like poles ATTRACT.
e) None of the above.
c) Unlike poles ATTRACT and like poles REPEL.
100
State the law of conservation of energy.
Energy cannot be created or destroyed.
100
Why can't most machines be 100% efficient?
a) Because of heat dissipation.
b) Because of heat expiration.
c) Because of chemical dissipation.
d) Because of chemical expiration.
a) Because of heat dissipation.
100
A light bulb uses 150 J of energy to create 30 J of light energy. How many joules of energy were lost as thermal energy?
120 joules
150 J - 30 J = 120 J
200
Which of the following describes mechanical energy transforming into chemical energy?
a) Playing drums to create sound.
b) Hammering a nail.
c) Using two rocks to create a fire.
d) Chewing food to digest in your body.
d) Chewing food to digest in your body.
200
What does AC and DC stand for?
What is the difference between the two?
Direct Current and Alternating Current.
DC is where electricity flows in only one direction.
AC is where electricity flows back and forth many times per second.
200
A lightbulb uses 150 J of electric energy to produce 30 J of light energy. What is the lightbulb's efficiency?
a) 25%
b) 0.2%
c) 20%
d) 0.25%
c) 20%
30J/150J x 100 = 20%
200
Which statement is TRUE?
a) Efficiency is measured in percentage from 0.0% to 0.99%
b) Efficiency is measured in percentage from 0% to 100%
c) It is impossible to have a 99.999% efficient device.
d) Efficiency is measured with the formula input/output.
b) Efficiency is measured in percentage from 0% to 100%
200
What energy transformation is taking place in the scenario below?
Electrical energy to thermal energy.
300
What does the OTEC stand for?
a) Ocean Thermal Electrical Conversion
b) Oceanic Terminal Electrical Conversion
c) Ocean Thermal Energy Conversion
d) Oceanic Temperature Energy Conversion
c) Ocean Thermal Energy Conversion
300
What are three main parts of a generator and motor?
a) commutator, stator and rotor
b) commutator, armature and brushes
c) commutator, armature, rotor
d) commutator, armature and stator
b) commutator, armature and brushes
300
A 10W oven is plugged into an outlet that produces a 2.5A current. Calculate the voltage.
a) 25V
b) 25A
c) 4A
d) 4V
d) 4V
10 / 2.5 = 4V
300
Which of the following pictures above is more efficient and why?
The second picture, because it has less moving parts and therefore creates less friction.
300
Which device would become more efficient from increasing bearings and lubricants?
a) a fridge
b) a toaster
c) an iPhone
d) a car
d) a car
400
Name three energy transformations taking place in the above situation.
1. Muscles pushing from stored body energy (chemical) -> moving forward (mechanical)
2. Electric motor (electrical) -> cutting blade (mechanical)
3. Blade turning (mechanical) -> friction (heat)
4. Straining muscles (chemical energy) -> sweating (thermal energy)
400
Which of the statements is TRUE?
a) A generator converts mechanical energy to electrical energy.
b) A generator converts electrical energy to mechanical energy.
c) A motor converts chemical energy into thermal energy.
d) A motor converts thermal energy into electrical energy.
a) A generator converts mechanical energy to electrical energy.
400
Calculate the joules created from a 12W toaster that is used for 1 minute.
720 J
E = Pt
1 minute = 60 seconds
12W x (60 seconds) = 720 J
400
Comparing efficiencies between similar devices allows us to:
a) judge both environmental impact and voltage
b) judge both power and voltage
c) judge both environmental impact and energy cost.
d) judge both joules and energy cost.
c) judge both environmental impact and energy cost.
400
If you want to save money, which toaster would be best for you?
a) A low wattage toaster because it converts energy faster.
b) A low voltage toaster because it converts energy slower.
c) A low wattage toaster because it converts energy slower.
d) A high wattage toaster because it converts energy slower.
c) A low wattage toaster because it converts energy slower.
500
What is a thermocouple and what does it do?
a) A thermocouple can be used to measure temperature and converts thermal energy into chemical energy.
b) A thermocouple can be used to measure temperature and converts thermal energy into electrical energy.
c) A thermocouple is used to increase resistance and converts chemical energy into mechanical energy.
d) A thermocouple is used to increase voltage and converts thermal energy into mechanical energy.
b) A thermocouple can be used to measure temperature and converts thermal energy into electrical energy.
500
Answer the following:
a) Describe what a transformer is.
b) When is it a good idea to use a STEP-UP transformer?
c) When is it a good idea to use a STEP-DOWN transformer?
A transformer is a device that changes the amount of voltage.
- Step-Up Transformers are good for efficiency (carrying current along long distances)
- Step-Down Transformers are good for safety (making the electricity safe for households and daily use)
500
Based on the P = IV and E = Pt formulas, name ALL the units used for each of the following abbreviations:
P = ? (2 units) E = ? (2 units)
I = ? t = ? (2 units)
V = ?
P: Watts or kilowatts E: Joules or kWh
I: Amps t: s or h
V: Volts
500
Which of the following would be the most energy efficient when considering electricity bills?
a) Washing clothes by hand.
b) Washing clothes with an 1000W machine.
c) Washing clothes with a 500W machine.
d) Washing clothes with a 1500W machine.
a) Washing clothes by hand.
500
A 3000W lamp is left on for 90 minutes. Calculate the Kilowatt hours.
a) 4.5 kW h
b) 45 kW h
c) 90 kW h
d) 5 kW h
a) 4.5 kW h
3000W = 3kW
90 minutes = 1.5 hours
3 x 1.5 = 4.5 kW h