YOU WERE LOOKING FOR: Static Electricity Practice Test Answers
Ms Jo Jo rubbed two balloons with a piece of wool. What will happen when the balloons are brought near each other? The balloons will attract each other. The balloons will pop.
Page No Question Give reasons for the following: a Your hair stands on its ends while removing a sweater or when you pull off your hat. Answer: a Our hair stands on end while we remove a sweater or our hat because it acquires static electricity...
This is because the glass rod is positively charged, and so the near end of the electroscope rod acquires the opposite charge, i. However, the far end becomes positively charged, and the leaves of the electroscope diverge. What is the method of charging in A and B known as? Figure Answer: When C is brought near B, B acquires a positive charge by the process of induction, whereas, when C is brought near A, A acquires a negative charge by the process of conduction. Page No Question Two charged bodies A and B were each brought near an electroscope as shown.
When A is brought near the electroscope, the leaves of the electroscope diverge further. When B is brought near the electroscope, the leaves of the electroscope collapse. Give reasons and identify the charges on A and B. Figure Answer: When A is brought near the electroscope, the leaves of the electroscope diverge further, because A is positively charged.
When A is brought near the electroscope, more negative charge starts accumulating on the disc of the electroscope by the process of induction, whereas the far end becomes more positive, so the leaves of the electroscope diverge further. When B is brought near the electroscope, the leaves of the electroscope collapse, because B is negatively charged. When B is brought near the electroscope, the negative charge on the disc of the electroscope starts moving towards the leaves of the electroscope by the process of induction, so the leaves of the electroscope becomes less positive and collapse. Page No Question A metal ball mounted on an insulated stand is given an electric charge.
It is then touched with a rod, one end of which is held in the hand. What happens to its charge if the rod is made from one of these materials?
They both involve electric charges. In this chapter, you will review the buildup of electric charges, or static electricity. In the next chapter, you will review the flow of electric charges as current through circuits. Electric Charge Matter is made up of atoms, which in turn are made up of particles. One of those particles, the electron e , carries a negative electric charge. The symbol for charge is q, and the SI unit of charge is the Coulomb C. The charge of an electron is —1. A proton carries a charge that is equal in magnitude to that of an electron, but has a positive value of 1. In addition to electrons and protons, neutrons are also found within atoms. Neutrons are electrically neutral. Objects become charged when electrons are transferred from one to another. Objects described as negatively charged have a surplus of electrons, whereas objects described as positively charged have a deficiency of electrons. Charges are conserved whenever they are transferred, which means that electric charges are neither created nor destroyed.
For example, when a rubber rod is stroked with a piece of wool, electrons are transferred from the wool to the rubber. As a result, the rubber rod becomes negatively charged because it gains electrons and the wool becomes positively charged because it loses electrons. Conversely, if a glass rod is rubbed with a piece of silk, electrons are transferred from the glass to the silk. In this case, the glass rod becomes positively charged because it loses electrons, and the silk becomes negatively charged because it gains electrons.
In each case, the net loss of electrons by one object equals the net gain of electrons by the other object. Charge is conserved. The law of charges states that unlike charges attract one another, and like charges repel one another. The same is true for charged objects such as the rods and cloths described earlier. The law of charges is easily demonstrated with the use of pith balls suspended from strings thin enough to be considered massless. Two positively charged pith balls or two negatively charged pith balls will repel one another. A positively charged pith ball and a negatively charged pith ball will attract one another. The magnitude of the force between charged particles FE is proportional to the product of the two charges q1 and q2 and varies inversely as the square of the distance between them r2.
If calculations are required, you will be provided with the value of k. Example: Two point charges q1 and q2 are separated by distance r. What happens to the electric force between these two charges if the distance is halved? The force is quadrupled. Electroscope An electroscope is an instrument used to determine the presence of small electric charges. It consists of two thin metal leaves suspended from a metal knob. The metal leaves hang down when not charged. When a negatively charged object is brought near the metal knob at the top, the electrons in the knob are repelled into the leaves.
The knob becomes positively charged and both leaves become negatively charged. Because the same charge is transferred to each leaf, they repel one another and separate. If, instead, a positively charge object is brought near the metal knob at the top, electrons are drawn into knob. The knob becomes negatively charged, and the leaves become positively charged. Again, the leaves have the same charge, so they repel one another and separate. Electric Field An electric field exists in the space around an electric charge where another charge will experience a force.
An electric field can be visualized by drawing arrows known as electric field lines. Each line points in the direction in which a positive test charge would experience a force. A positive test charge would be repelled by a positive charge, so the electric field lines point outward from a positive charge. A positive test charge would be attracted toward a negative charge, so the electric field lines point inward toward a negative charge. When two charges are brought near one another, the lines become curved as shown in the following diagram. The lines curve away from like charges and toward unlike charges.
The magnitude of the electric field is known as the electric field intensity E. Another way to describe this quantity is as the force per unit charge in a region of space. The relationship is described by the following equation. Therefore, you can rewrite electric field intensity as shown here. Viewing the equation in this format shows that the electric field at a given point depends on the charge of the object establishing the field and the distance to a point in space. Electric Potential Moving a charge against an electric field requires work. The work required to move charge q between two points in an electric field is known as potential difference V.
The SI unit of work is the joule, and the unit of charge is the Coulomb, which makes the unit of electric potential the joule per coulomb, or volt. Potential difference is essentially the same as electric potential. For electric potential, however, the work is defined as the amount required to bring a positive charge from infinity to some point. You will read more about electric potential in your review of electric circuits. Test-Taking Hint When answering questions, make sure you read through all the answer choices before deciding. Two answer choices may be very similar, so you could overlook the difference if you rush to choose one. How does the charge of an electron compare to the charge of a proton?
A the charge of a proton is double the magnitude of the charge of an electron. B the charge of a proton is the same as the charge of an electron. C the charge of a proton is equal and opposite to the charge of an electron. D the charge of a proton is half the magnitude of the charge of an electron. E the charge of a proton is four times charge of an electron. Two point charges q1 and q2 are separated by distance r. What happens to the electric force if the charges are doubled? A it is quartered. C it remains the same. D it is doubled. E it is quadrupled. Particle A with charge q exerts a force F to the right on a particle B with a charge of —2q. What is the magnitude and direction of the force exerted by particle B on particle A? The electric force between two charges is negative. Which of the following statements must be true? A Both charges must be positive. B Both charges must be negative. C One charge must be twice the magnitude of the other.
D The force must be directed toward the larger charge. E The force between the particles must be attractive. The diagram below represents the electric field between two point charges. What must be true about the charges? A A is positive and B is negative. B A is positive and B is positive. C A is negative and B is negative. D A is negative and B is positive. E A is neutral and B is neutral. A rod is brought near the knob of an electroscope. The metal leaves separate. What can you conclude about the rod? A It was electrically charged. B It was electrically neutral. C It was electrically negative. D It was electrically positive. E It was a source of electrons. Charge q establishes an electric field. What is the magnitude of the electric field strength at a distance of 80 cm away?
This quiz is incomplete! To play this quiz, please finish editing it. Delete Quiz This quiz is incomplete! Why can you get a shock if you touch a metal doorknob after walking across a wool carpet? You have gained neutrons; the doorknob has fewer electrons. You have lost electrons; the doorknob has many electrons. You have gained electrons; the doorknob has many electrons. Ms Jo Jo rubbed two balloons with a piece of wool.
What will happen when the balloons are brought near each other? The balloons will attract each other. The balloons will pop.
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An example would be if a balloon has the opposite charge as someone's hair, and they are held near each other. The hair will stand up and stretch out towards the balloon because the opposite charges are attracted to each other. She generates a negative charge and reaches to touch the positively charged doorknob. Static electricity is formed. What will happen when she touches the doorknob? Possible Answers: She will not be shocked because of the opposite charges. Nothing will happen; it is just a doorknob that she is touching. She will be shocked because of the opposite charges. She will be shocked because of similar charges. Correct answer: She will be shocked because of the opposite charges. Explanation: When someone rubs their feet across the carpet, there is a build-up of static electricity. Your feet are rubbing negatively charged electrons off of the floor, and it leaves you with a slightly negative charge.
When you reach the positively charged knob, the electrons jump and cause the static shock that you feel on your fingertips. The opposite charges are attracted to each other. Figueroa's class is exploring the cause and effect relationships of electricity. He asks the class to think about a balloon being rubbed on someone's hair and then held up to small bits of paper. Which of the following is true regarding the static electricity between the paper and the balloon?
Possible Answers: The two objects must be touching each other to be attracted. The two objects must be different colors to have an electric pull. The two objects can have the same electric charge and still be attracted. The two objects can be separated and still attracted to each other. Correct answer: The two objects can be separated and still attracted to each other. Explanation: Mr. Figueroa is providing an example of how two objects do not need to be touching for there to be an attraction. The static electricity generated by rubbing the balloon on someone's hair is the opposite charge as the charge on the paper. When the paper and balloon come near each other not touching , the different charges are attracted to each other, and the balloon will cause the paper to "jump" or move.
What happens when you put the balloon near your hair? Possible Answers: Your hair is attracted to the balloon and lays flat. Your hair is repelled by the balloon and stands up. Your hair is repelled by the balloon and lays flat. Your hair is attracted to the balloon and stands up. Correct answer: Your hair is attracted to the balloon and stands up. Explanation: When static electricity is created between a balloon and your hair, your hair is attracted to the balloon. If you rub the balloon on your hair and move it away slowly, your hair will follow the direction of the balloon and stick straight out. Your hair is the opposite charge of the balloon. Opposite charges attract, so the hair and balloon are attracted to each other. My socks are attached to my shirts, and when I pull them apart, I hear a crackling noise. Why are the socks attracted to each other?
Possible Answers: They always want to be with their match. They have no charges. They have the same charge. They have opposite charges. Explanation: The reason this happens is because of static electricity. In the dryer, different fabrics rub together, the electrons from a cotton sock may rub off onto a polyester shirt. That's why clothes sometimes stick together. They have opposite charges which are attracted to each other. Possible Answers:.
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