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When is an object positively charged? When is an object negatively charged? How to identify a positive or negative charged object. Applications of electrified objects in life. Some questions reinforce knowledge about electrified objects.

When is an object positively charged and when is an object negatively charged? An object becomes positively charged when it lacks electrons. An object becomes negatively charged when it has an excess of electrons. What are the effects of electric current? This is the basic knowledge of the general physics program. The following article will help you learn more about electrified objects.

1. When is an object positively charged?

An object becomes positively charged when it loses electrons.

Example: Rubbing a plastic ruler on a dry piece of cloth, after rubbing, the cloth loses electrons, so it becomes positively charged.

2. When is an object negatively charged?

An object becomes negatively charged when it gains an additional electron. In other words, when the number of electrons is greater than the number of protons.

For example: Rubbing a plastic ruler against a piece of dry cloth, after rubbing, the plastic ruler receives more electrons from the cloth, so the plastic ruler becomes negatively charged.

3. How to identify a positive or negative charged object:

Electrification is the accumulation of electrical charges on the surface of a non-conductive material.

Many objects, after being rubbed, have the ability to attract other objects.

– Many objects, after being rubbed, have the ability to light up the lamp of the electric tester.

– An electrically charged object, when rubbed, has the ability to attract other objects;

– When an electrically charged object is rubbed, it is capable of brightening the electric tester;

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Based on the characteristics of an electrified object, it is capable of attracting other objects or releasing sparks to other objects, so if we want to know if an object has been electrified or not, we need to bring the object to be recognized.

You can easily see phenomena electricity in everyday life. Such as:

– On cold days, you often wear a hat to keep warm when going outside. Then remove the hat, you can easily see the hair being sucked inside the hat. It is between the hair and the hat that are electrified.

– In hot weather, when you use a comb to melt your hair, you will find that the hair is attracted by the comb and pulled straight out.

When you brush, you accidentally create friction between the comb and your hair, so both are electrified.

– Long-term use of electric propellers has a lot of dust on the edge of the propeller. If you see dust on the surface of the table, you can easily blow it away. While the propeller rotates very strongly, it does not push the dust, even being stuck in reverse. The explanation for this phenomenon is also electrification due to friction.

In fact, there are many impurities and dust in the air. As the propeller rotates, it frictions with the air.

Specifically, dust particles that are invisible to the naked eye. Becoming an electrically charged object, the propeller attracts dust particles in the air. Make them stick to the edge of the propeller. Accumulating more and more so we can see clearly.

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Light objects:

If it attracts light objects, then the object is electrified.

If it can’t attract a light object, the object is not electrified.

Example: When we blow the dust, the dust flies away. The electric fan blows strong wind, but after a while there is a lot of dust clinging to the propeller ⇒ The propeller rubs a lot against the air, so it becomes electrically charged ⇒ The propeller sucks dust particles.

Other items:

If there is an electrical discharge, the object is already electrified.

If there is no discharge, the object is not charged.

Example: Rub the piece of plastic film with a dry cloth. Place the corrugated sheet on top of the plastic film. Touch the electric tester to the piece of corrugated iron ⇒ The electric tester flashes ⇒ There is a spark through the electric tester ⇒ The plastic film is electrified.

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4. How to make an object electrified:

An object can become electrified in many different ways, the simplest of which is electrification by rubbing. Many objects, when rubbed, become electrified.

4.1. Make an object electrified by contacting another object:

Between a charged object and an uncharged object. When these two objects are brought into contact
(not rubbing or creating friction) but simply put very close to each other or overlap, the other object will be electrified with the same sign as the electrified object.

The free charges (specifically electrons) inside the charged object move to the uncharged object. Causing both of them to be electrified.

4.2. Make an object electrified by responding:

When a positively charged object is brought close to a charge neutral metal rod AB. At this time, when testing, it will be found that the A end of the metal rod is positively charged, and the B end will be negatively charged if the B end is located near a positively charged object.

If A is near a positively charged object, then A is negatively charged and B is positively charged.

We see that any electrically neutral object when in close contact with a charged object, the two ends of the neutrally charged object will be charged with opposite charges, the end near the charged object will have a charge. opposite sign to the charged object.

This phenomenon is called reactive electrification or electrostatic induction.

4.3. Make an object electrified by rubbing:

Simple experiment that proves an object can become electrified

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Use a plastic ruler, scraps of paper, plastic crumbs, or a small ball made of styrofoam.

Bring one end of the plastic ruler close to samples of paper or plastic scraps or foam balls, observe nothing happens.

Rub one end of the plastic ruler with a dry cloth, and then bring the end close to a piece of paper, plastic, or a sponge ball. Observation will see the phenomenon of these paper and plastic debris clinging to the plastic ruler that has been rubbed with cloth. In other words, the tip of the plastic ruler attracts these small particles.

Objects after being rubbed will have the ability to attract other objects, becoming electrified objects.

To check whether the object after being rubbed is really electrified, you can use an electric tester to check or observe whether they attract other small objects.

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5. Applications of electrified objects in life:

The study of electrified objects helps us to explain phenomena in life and apply them in daily life such as making lights on, warming water to boil, etc.

Electrically charged objects can be applied in technical life, for example:

– Tankers carrying petrol and oil often have an iron chain, one end attached to the tank shell, the other end hanging on the road surface when the vehicle is running. Doing so reduces the risk of an electrical charge causing a gas tank to explode. When a gasoline tanker is operating on the road, due to the friction between the fuel tank and the air, the fuel tank becomes electrified. If the charge is too large, it will cause a fire. Therefore, the gas tank has a chain that drags on the ground to neutralize the amount of charge that has adhered to the fuel tank to avoid the phenomenon of fire.

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– When cleaning the glass, the cloth that we use to wipe rubs with the glass surface, then the glass becomes electrified, so it attracts the adhesions, so we see that the glass surface is dusty after cleaning.

– When a charged metal ball is brought close to a conductor, the far end of the sphere is charged with the same sign as the sphere, and the end near the sphere is charged with the opposite sign.

– When you comb your hair with a plastic comb, you will see that the hair extensions are pulled up (due to the friction between the hair and the comb causing an electrical charge, so the plastic comb has the ability to attract hair).

6. Some exercises to consolidate knowledge about electrified objects:

Question 1: After a period of operation, the propeller gets a lot of dust because:

A. The propellers rub with the air and become electrified, so they attract a lot of dust.

B. The impeller is damp, so it sucks up a lot of dust.

C. Some slime in the air settles on the fan blades and sucks up a lot of dust.

D. Colloidal dust should stick to the propeller.

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Answer A: After a period of operation, the propeller gets a lot of dust because it rubs with the air, becomes electrified, so it sucks up a lot of dust.

Question 2: The car runs for a long time. After getting off the car, touching the side of the car, sometimes it feels like an electric shock. The reason is due to:

A. The electrical part of the vehicle is damaged.

B. The car’s walls rub against the air, so the car becomes electrified.

C. Due to some electrical appliances nearby working.

D. Because there is going to be a thunderstorm outside.

Answer B: The car runs for a long time because the car’s wall rubs against the air, so the car is electrified, touching the wall of the car sometimes feels like an electric shock.

Question 3: In some industries manufacturing, sparks are often seen between the pulley and the pulley. Explain why?

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A. Pulleys and pulleys become electrified by rubbing.

B. The pulley and the zipper get hot from rubbing.

C. The temperature in the room then rises.

D. Due to strong rubbing.

Answer A: In some manufacturing industries, sparks are often seen between the zipper and the pulley because when working due to friction, the pulley and the zipper are electrified.

Question 4: When the flat piece of metal attached to the tip of the electric tester touches the piece of polyethylene that has been rubbed many times with wool, the bulb of the electric tester lights up when touching the tip of the finger because:

A. There is electricity in the pen.

B. Finger touches the tip of the pen.

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C. Pieces of polyethylene have become electrified by rubbing.

D. Electrically charged piece of corrugated iron.

Answer C: The bulb of the electric tester lights up when the finger touches the tip of the pen because then the polyethylene piece is electrified by rubbing, the charge passes through the aluminum piece to the electric tester.

Question 5: Which of the following statements is incorrect?

A. All objects are capable of electrification.

B. The Earth attracts objects so it is always electrified.

C. Many objects, after being rubbed, become electrically charged objects.

D. It is possible to electrify many objects by rubbing.

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Answer B: Wrong conclusion: Earth attracts objects so it is always electrified

Question 6. In a cold country, in winter, a person wears socks (socks) on a carpeted floor, when he puts his hand near the metal doorknobs, he hears a small click and his hand electrocution. Please explain why?

A. Because when walking on the carpet, there is rubbing with the carpet, so it is electrified.

B. Due to the phenomenon of electric discharge between the person and the door handle.

C. Both A and B are wrong

D. Both statements A and B are correct.

Answer D: In a cold country, in winter, a person wears socks (socks) on a carpeted floor, when he puts his hand near the metal doorknobs, he hears a small click and a human hand that was electrocuted.

The reason for this is because:

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+ When walking on the carpet, there is rubbing with the carpet, so it becomes electrically charged => hear a small crackle

+ When you put your hand on the metal doorknob due to the phenomenon of electric discharge between the person and the doorknob => that person’s hand is electrocuted.

Based on the characteristics of an electrified object, it has the ability to attract other objects or discharge sparks to other objects. So if we want to know if an object is electrified or not, we need to bring the object to be distinguished. Mastering the principles of negatively charged and positively charged objects will help you better apply and explain phenomena in daily life.

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