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Exercise C1 Solution Page 37 Physics 9 Textbook
Problem:
Observing Figure 13.1 and state:
+ In which electrical devices and equipment does electric current perform mechanical work?
+ In which electrical devices and equipment does electric current supply heat energy?
Solution:
+ Electric current performs mechanical work in the operation of electrical tools and devices: Drills, water pumps.
+ Electric current supplies heat energy in the operation of electrical tools and devices: Electric rice cookers, soldering irons, irons.
Exercise C2 Solution Page 37 Physics 9 Textbook
Problem:
All electrical devices convert electrical energy into various forms of energy. Identify the forms of energy transformed from electrical energy in the operation of each electrical device in table 1.
Table 1:
Solution:
Exercise C3 Solution Page 38 Physics 9 Textbook
Problem:
Identify in the operation of each electrical device in table 1, which energy component transformed from electrical energy is useful and which is useless.
Solution:
Exercise C4 Solution Page 38 Physics 9 Textbook
Problem:
From the knowledge acquired in grade 8, explain the relationship between work A and power P.
Solution:
Power P is the characteristic quantity for the rate of work done, determined by the work done in a unit of time:
where A represents the work done in time t.
Solving exercise C5 on page 38 SGK Physics 9
Problem:
Consider a circuit placed under potential difference U, with current I flowing through it and the electrical power of this circuit being P. Show that the work done by the electric current in this circuit, or the electrical energy consumed by this circuit, is calculated by the formula A = Pt = UIt,
Where U is measured in volts (V),
I is measured in amperes (A)
t is measured in seconds (s)
then the work A of the electric current is measured in joules (J)
1 J equals 1 watt-second equals 1 volt-ampere-second.
Solution:
Solving exercise C6 on page 39 of Physics 9 textbook
Problem:
Table 2 records the meter readings when using various electrical appliances.
Table 2:
From this table, determine the amount of electrical energy corresponding to each increment in the meter reading (each increase of 1 unit in the meter reading).
Solution:
Each increment in the meter reading corresponds to 1 kWh of electrical energy used.
Solving exercise C7 on page 39 of Physics 9 textbook
Problem:
A light bulb labeled 220V - 75W is continuously lit with a voltage of 220V for 4 hours. Calculate the amount of electrical energy used by this light bulb and the meter reading in this case.
Solution:
Since the light bulb is used with the rated voltage, the power consumed by the bulb is also equal to the rated power.
The amount of electrical energy used by this light bulb is: A = Pt = 75 * 4 * 3600 = 10800000 J = 0.3 kWh
Alternatively, we can calculate in kWh units: A = Pt = 0.075 * 4 = 0.3 kWh.
So, the electric meter reading in this case is 0.3 units.
Solving exercise C8 on page 39 of Physics 9 textbook
Problem:
An electric stove operates continuously for 2 hours at a potential difference of 220V. During this time, the electric meter reading increases by 1.5 units. Calculate the amount of electrical energy used by the electric stove, the power of the electric stove, and the current intensity flowing through the stove during the specified time.
