Vì sao phải truyền tải điện năng đi xa?

The knowledge in the transmission of electricity is greatly applied in the sacrifices. Besides, this is also a key exercise in the exam preparation section for good students in Physics 9. The following article will mention the most necessary content, helping them to train and improve thinking skills.

View All

Why must transmit electricity far away?

The demand for electricity of households is increasing now. All daily activities are mostly needed to use electricity.

However, because of the nature of electricity and to ensure safety for everyone, the generator cannot be near households. Therefore, to transmit electricity to go far to meet the needs of every home. As well as when transmitting electricity far away, to reduce electricity waste better

At the same time, when you need to transmit electricity far away, it will be with the transmission lines. People do not use one -way current but will use alternating current for transformers. The reason is because the operating process of the transformer is based on the phenomenon of electromagnetic induction. This shows that if the phenomenon of electromagnetic induction, the word through the coil must be variable. Therefore, only alternating current makes the magnetic flux variables.

The waste of electricity on the electric transmission line

In the process of transmitting electricity traveling far by wire, there is a part of the power consumption. The reason is because the appearance of heat radiating on the line.

Calculate the waste power on the electrical transmission line

Formula for transmitting electricity:

P = UI

The formula for calculating the waste power on the guide line:

In there:

• P: is the power to be transmitted.

• U: is the voltage of the two ends of the transmission line.

• I: is the current of the electric load line.

• R: is the resistance of the power line.

Note: From the formula for calculating the waste power, drawing the capacity is concluded by the waste power due to heat radiation on the power line inversely proportional to the square of the voltage of the two ends of the electric line.

How to reduce waste

The way to reduce waste on the power line is to increase the voltage of the two ends of the wire. This is considered the most optimal and effective way, applied in reality.

Note: The random transformer consists of only a conductor coil with many outputs. Based on the power source and the consumption load connected to the head of the coil, the machine will perform low voltage or increased function. If the load is connected to the end of A, C and the power source connected to A and B, the machine will be lowered and vice versa. (See the illustration below)

The role of transformer in the transmission of electricity is far away

The transformer, also known as the transformer, is a static electromagnetic device, operating based on the principle of electromagnetic induction. The device is capable of transforming an alternating current system at this voltage into an alternating current system at a voltage different from the same frequency.

So what role does the transformer play in the process of transmitting electricity far away? If the machine has any problems, it is easy to lead to power loss and make it difficult to transmit electricity to households. In a more understandable way, the transformer is an electromagnetic device that uses the principle of electromagnetic induction for the purpose of transmitting, bringing electrical energy or alternating electrical signals between the circuits operating according to a certain principle.

The transformer includes the following main parts:

• MBA steel core: Used to guide pine, often using good magnetic materials to make.

• MBA winding: usually made from aluminum or copper, capable of receiving energy to transmit energy.

• MBA shell: Including lids and barrels.

• MBA box: Steel core, MBA oil and winding, performing the task of increasing insulation and radiating heat to the environment.

• MBA lid: has the main task of insulation.

• Insurance tube: often made of steel, keeping the MBA from being broken due to oil spill.

Exercise on electricity transmission away from Ly 9 Lesson 36

The following are exercises on the transmission of electricity, helping them to understand the theory and apply the knowledge learned to solve the calculation exercises as well as explain the phenomena in reality.

Question 1: To transmit the same power capacity, if the power line is shortened 4 times, the capacity wastes because of the heat will:

A. Discount 2 times

B. Increase 2 times

C. Discount 4 times

D. Increase 4 times

Solution: Answer C

Explanation: When the transmission line is shortened 4 times, the wire resistance also decreases 4 times, so the waste of heating on the transmission line also decreases 4 times.

Question 2: When transmitting the same electricity, want to reduce the waste capacity because of heat radiating, which way people often use in the following ways?

A. Reducing the resistance of the line

B. Reducing transmission voltage

C. Increase the transmission voltage

D. Increase the resistance of the line

Solution: Answer C

Explanation: People often increase the voltage placed in the two ends of the wire to reduce the waste due to heat generation when transmitting electricity away. This is also considered the most effective and optimal way.

Question 3: People need to transmit electricity from the power plant to the residential area. Initially the power capacity was 100kW, but then due to the need to use, the power transmitted power increased to 200kW. Waste due to the transmission process changes like?

A. Increase 2 times

B. Increase 4 times

C. Discount 2 times

D. reduced 4 times

Solution: Answer B

Explanation: Based on the formula for calculating the waste power P (HP) = RP^2/U^2. We see that when the transmission power increases to 2 times, the waste of transmission increases to 4 times

Question 4: To transmit the same electricity capacity, if the power line increases twice, the power capacity increases by 2 times, the power consumption because the heat will be heated:

A. Increase 2 times

B. Increase 4 times

C. Increase 8 times

D. increased to 16 times

Solution: Answer C

Explanation: Based on the formula for calculating the power consumption P (HP) = RP^2/U^2, we see when the transmission capacity increases to 2, the conductor resistance increases 2 times, the transfer cost increases by 8 times.

Question 5: When transmitting electricity from the power plant to the place of consumption, it is calculated that the capacity is wasted by the transmission of 10kW. But due to the change in demand, people must power up to 2 times. If you want to waste it, it is still 10kw, people must

A. Increase the conductor section 2 times

B. Reduce the cross -section of the conductor 2 times

C. Increase the transmission voltage to 1.41 times

D. Increase the transmission voltage 2 times

Solution: Answer D

Explanation: Based on the formula for calculating the power consumption of power P (HP) = RP^2/U^2, when the power P increases 2 times and the voltage transmission u is 2 times, the cost of wastage does not change.

Question 6: Based on the formula for calculating the waste power due to heat generation during the power transmission process, please state the two measures that can be applied to reduce the waste capacity when transmitting a definite power capacity?

Solution:

• The first measure: Increasing transmission voltage. This is the most optimal and effective way

• The second measure: Reducing the wire resistance (reducing the length, increasing the cross -sectional cross section, using good conductive materials)

Question 7: The electricity line from the hydroelectric plant to the site of 120km long. The conductor is made of copper, with R = 0.4Ω. The current measurement of the current on the conductor is 200A. Calculate the waste capacity on the line?

Solution:

The conductor resistance is: R = 120.0.4 = 48 (Ω)

The waste capacity on the line is:

P (HP) = Ri^2 = 48,2002 = 1920000 (W)

Question 8: People need to transmit a 100kw electric power under an effective 5kV voltage. During the transmission process, the capacity of the waste is measured on the line is 10kW. What is the resistance of the conductor?

Solution:

Change 100kW = 100000W; 10kW = 10000W; 5KV = 5000V

So the resistance of the conductor is 25Ω

Question 9: People transmit alternating current from the generator station is 15km from the resort with a metal conductor with a crazy impedance p = 4.10-7 Ωm, cross section 0.5cm2. The voltage and capacity at the station are 10KV and 600KW. Calculate the power radiating power on the line during electricity transmission.

Solution:

Change 15 km = 15000m; 10kV = 10000V; 600kW = 600000W; 0.5cm2 = 0.5.10-4m2

The resistance of the entire conductor is:

The heat radiating power on the conductor is:

Question 10: Know the power capacity of the factory is 55 kW, the distance from the production site to the consumption is 100 km, the conductor has a total resistance of 60Ω

a) Calculate the waste capacity because the heat radiating on the load line in two cases:

• The voltage of the two ends of the power line is 500V.

• The voltage between the two ends of the power cord is 50kV

b) Please comment on the results of the above 2 cases

Solution:

a) The current of the conductor is: I = P/U = 55000/500 = 110 (a)

Costed capacity: P (Hp) = Ri^2 = 60. 110^2 = 726000 (W)

The current on the line is: I ‘= P/U’ = 1.1 (A)

Costed capacity is: P ‘(HP) = R.I’^2 = 60.1,1^2 = 72.6 (W)

b) We see: u ‘/u = 50000/500 = 100

P/P ‘= 726000/72.6 = 10000

Conclusion: The voltage before transmission increased to 100 times, the capacity of wasted loss decreased by 10000 times.

Question 11: One of the options for reducing electricity waste on the power line is to reduce the resistance of the conductor. What is this disadvantage?

A. Must make a wire with a large cross section.

B. Very large amount of color metal.

C. Must have a large electric pole system.

D. Options A, B, C are all disadvantages.

→ Answer D

Question 12: On the same load line, there is the same power P, when using a 500kV voltage, the consumption power is P1; When using the 1000V voltage, the consumption power is P2. P2P1 ratio can receive out of the following results:

A. 250000.

B. 25000.

C. 2500.

D. 250.

→ Answer A

Question 13: 100km long power line, transmitting a 300A current. Bronze conductor every 1km with resistance 0.2Ω. Which of the following is the capacity of heating due to heat on the wire?

A. PHP = 1800000KW.

B. PHP = 1800000W.

C. PHP = 1800000J.

D. PHP = 180000KW.

→ Answer B

Question 14: To transmit a power capacity, if the power line is 3 times, the power is wasted because the heat will

A. Increase 3 times.

B. Increase 9 times.

C. Discount 3 times.

D. decreases 9 times.

→ Answer A

Question 15: What is the purpose of building a North -South power line with a voltage of up to 500kV for?

A. Simply to transmit electricity.

B. To avoid environmental pollution.

C. To reduce electricity waste.

D. To perform electrical safety.

→ Answer C

Building a solid mathematical platform for children from an early age with a multimedia, extremely cheap cost less than 2k/day with Mầm non Cát Linh Math.

Knowledge related to the transmission of electricity has been updated and accurate by Mầm non Cát Linh. Hopefully the article has provided useful information, helping them achieve many good results in the process of self -study Physics 9.

Nguồn: https://mncatlinhdd.edu.vn/ Tác giả: Nguyễn Lân dũng