1. Measurements show that there is an electric field surrounding the Earth. Its magnitude is about 100 N/C at the Earth's surface and points inward toward the Earth's center. From this information, can you state whether the Earth is negative or positive?
(Planet Earth is negatively charged, Planet Earth is electrically neutral, Planet Earth is positively charged or There is not enough information to decide.)
2. If you are caught outdoors in a thunderstorm, why should you not stand under a tree? Can you think of a reason why you should not stand with your legs far apart? Or why lying down can be dangerous? (Hint: Consider electric potential difference.)
3. If you rub an inflated balloon against your hair and place it against a door, by what mechanism does it stick? Explain.
4. When the chassis of a car is moved into a painting chamber, a mist of paint is sprayed around the chassis. When it is given a sudden electric charge and mist is arracted to it, presto - the car is quickly and uniformly painted. What does the phenomenon of polarization have to do with this?
Give them a try, and I will be happy to critique.
On the first one, Earth is mainly an insulator.
1. Based on the given information, we can conclude that the Earth is negatively charged. The inward direction of the electric field indicates that it is being attracted towards the center of the Earth, suggesting a negative charge.
2. Standing under a tree during a thunderstorm is not safe because trees are tall objects that can act as lightning attractors. Lightning tends to strike the highest point in the vicinity, and standing under a tree increases the risk of being struck. Additionally, trees can conduct electricity, so standing near one during a storm increases the chance of being injured by any lightning that strikes the tree.
Standing with your legs far apart is also not advised during a thunderstorm. Since lightning can travel through the ground, having a wide stance increases the likelihood of the electrical current passing through your body, potentially causing harm.
Lying down is dangerous during a thunderstorm because it increases the chances of current passing through your body from the ground. The current can flow across the ground's surface, and lying down provides more contact area, increasing the risk of injury.
The main concern in all these scenarios is the electric potential difference that can occur during a lightning strike. It is important to minimize the contact with conductive objects and reduce the potential for electricity to flow through your body.
3. The mechanism by which a rubbed balloon sticks to a door is called static electricity. When you rub the inflated balloon against your hair, electrons are transferred from your hair to the balloon. This transfer of electrons creates an imbalance of charges on the balloon's surface, giving it a negative charge.
When the negatively charged balloon is brought close to a neutral surface, such as a door, it induces a separation of charges in the door. The negative charge on the balloon repels the electrons in the atoms of the door, leaving the side of the door nearest the balloon with a positive charge. The attraction between the positive charges on the door and the negative charge on the balloon causes the balloon to stick to the door.
4. The phenomenon of polarization plays a crucial role in the painting process described. Polarization occurs when the atoms or molecules of a material become aligned in response to an external electric field.
When the chassis of the car is given a sudden electric charge, it creates an electric field around it. This electric field polarizes the mist of paint particles that are sprayed around the chassis. The paint particles become attracted to the charged chassis due to the polarization effect, resulting in a quick and uniform coating.
The charged chassis induces opposite charges in the paint particles, causing them to be attracted to the chassis. This phenomenon ensures that the paint particles are evenly distributed and adhere to the surface of the chassis, resulting in a uniform paint job.
1. To determine whether the Earth is negative or positive based on the given information about the electric field, we need to consider the direction of the electric field lines. The fact that the electric field points inward toward the Earth's center implies that the Earth is negative. This is because electric field lines originate from positive charges and terminate on negative charges. Therefore, we can conclude that the Earth is negatively charged.
2. Standing under a tree during a thunderstorm is not safe because trees act as lightning attractors and being directly under a tree increases the risk of being struck by lightning. When lightning strikes a tall object like a tree, the electrical discharge can follow the path of least resistance, which may include you if you are standing near the tree.
Standing with your legs far apart is also not recommended during a thunderstorm. This is because when lightning strikes the ground, it can create a potential difference between different points on the ground. If your legs are far apart, there is a greater chance that a potential difference will be created between your legs. This can lead to a dangerous electric shock passing through your body.
Lying down during a thunderstorm is also risky. While it is true that being in a lower position reduces the chances of being directly struck by lightning, it does not eliminate the risk entirely. Lightning can still travel through the ground and cause an electric shock if you are lying on it. Additionally, lying down on wet ground increases the risk because water is a good conductor of electricity.
3. The mechanism responsible for a rubbed balloon sticking to a door is called static electricity. When you rub the balloon against your hair, the friction between the balloon and your hair leads to a transfer of electrons. This causes the balloon to become negatively charged and your hair to become positively charged.
The negatively charged balloon then becomes attracted to the positively charged surface of the door. This attraction is due to the force of electric attraction between opposite charges. The balloon sticks to the door because the electric force between the charges overcomes other forces, such as gravity, that would normally cause the balloon and door to separate.
4. The phenomenon of polarization plays a crucial role in the car painting process described. Polarization occurs when the positive and negative charges in a material become separated, creating regions with an excess of positive or negative charges.
In the painting chamber, the mist of paint particles is sprayed around the chassis. These paint particles are typically uncharged. However, when an electric charge is suddenly applied to the chassis, it induces a separation of charges in the paint particles, causing them to become polarized.
The electric charge on the chassis attracts the polarized paint particles towards it, leading to an efficient and uniform coating of paint on the car. Without the polarization of the paint particles, they would not be strongly attracted to the electrically charged chassis, resulting in an uneven or incomplete paint job. Therefore, the phenomenon of polarization enhances the efficiency and quality of the car painting process.