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Check Your Understanding 9.2
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Gravity
Terms in this set (13)
What do we call the rate at which energy is transformed?
Power.
State one unit for energy and one unit for power.
energy - joules
power - watts, kilowatts
What is another name for joules per second?
Watts
In which unit are large amounts of energy measured?
Kilowatts
How many joules is 1 kW.h equal to?
10
State the relationship or energy (E), power (P) and time (t).
E = P/t
Two identical batteries are connected to different circuits. Explain how it is possible for batteries to supply different amounts of power.
Delivered power is the battery voltage squared divided by the resistance of the circuit, so if the two circuits have different resistances, the batteries will deliver different amounts of power.
Explain how two loads can consume the same amount of electrical energy but have different power ratings.
The power ratings can differ if the two loads have a different resistance.
What is the power rating of a light bulb if 3.0 A flow through it when connected to a 15 V battery?
45 Watts
How much electrical energy, in joules, does a 40 W light bulb consume in 15 min?
36,000 Joules
a) A 1600 W hair dryer is used for 15 min. How much electrical energy, in kW . h, did the hair dryer consume during this time?
a) 0.4 kW.h
b) If the cost of electricity is 7 cents/kW.h, how much did it cost to use the hair dryer?
b) 2.8 which is 3 cents
In a set amount of time, a battery supplies 25 J of energy to an electric circuit that includes two different loads. One of the loads produces 10 J of heat energy during this time interval. How much heat energy is produced by the second load in this time? Explain your answer.
10 J / second
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