Electricity Homework Doc- SNC1D-1

Electricity Homework Doc- SNC1D-1 1. Explain the difference between static and current electricity. The primary difference between static electricity and current electricity is that in static electricity, charges accumulate on the surface of the inductor. Current electricity is caused by electrons moving inside of the conductor. 2. State the laws of electrostatics. Law of Electrostatics says that like charges repel, opposite charges attract and charged objects will attract neutral objects. POS + POS = REPEL NEG + NEG = REPEL POS + NEG = ATTRACT NEG + POS = ATTRACT NEG + NEUTRAL = ATTRACT POS + NEUTRAL = ATTRACT 3. What are 3 ways to charge an object? Friction, conduction and induction. 4. Explain why when two objects are attracted to each other they may not be oppositely charged? An interaction between a positive and a negative charge will cause their forces to act in the same direction, from the positive to the negative. 5. If you rub plastic with wool which item becomes positively charged? As a result of friction produced when woolen cloth is rubbed against plastic, both wood and plastic become electrified. Thus, plastic has a greater electron affinity than wool, therefore, plastic acquires a negative charge, while wool acquires a positive charge. 6. If an object is charged by contact, what happens to the charge on both objects? Both objects acquire the same type of charge. If a negative object is used to charge a neutral object, then both objects become charged negatively. HMWK: Read 465-471 Q. 2-6,9 2. In your own words, define static electricity. Static electricity is the imbalance of electric charges within or on the surface of a material or between two materials. 3. (a) Which particle(s) are difficult to add to or remove from an atom? Atoms contain protons and neutrons, which are hard to add or remove. Due to the fact that both of these particles are confined inside the nucleus, they both contribute to the mass number of an atom.

As a result, whenever these particles are removed or added, the nucleus of an atom will be charged differently, therefore, its element will also be different. Hydrogen would become helium if a proton were added to its nucleus. (b) Which particle(s) are easier to add to or remove from an atom? An atom is quite easy to add or remove electrons since they are not really confined within the nucleus of the atom. The particles are far away from the nucleus, so they are not pulled tightly and closely to it. (c) How do your answers to (a) and (b) explain the formation of positively and negatively charged objects? The protons and neutrons of an atom are relatively hard to add to or remove from it, so they remain within the nucleus. The transfer of electrons is easier, and this is one of the factors that determines whether an object is positively or negatively charged. A positively charged object has a greater number of protons than electrons. Whenever an object gains more electrons than the number of protons present, it becomes negatively charged. 4. Describe the total charge on each of the following objects as either neutral, positive, or negative. Explain your reasoning. a) There is no charge on the object. The number of protons (+) is three and the number of electrons (-) is also three, resulting in the object being neutral. b) There are four negative charges and only three positive charges, resulting in a net charge of -1. 5. What would you do to the object in Figure 15 to make it neutral? Add two electrons to balance out the protons. 6. What would you do to the object in Figure 16 to make it positively charged? What would you do to the object in Figure 16 to make it negatively charged? Due to the fact that it is already neutral, any additional protons or electrons will result in a change in its charge. 9. Use diagrams to illustrate how a positively charged object can be used to induce a charge separation and attract a neutral object. When neutral objects become attracted to charged objects, induced charge separation occurs. Initially, the ball, as shown in the figure, is neutral; however, when a positively charged object comes near it, electrons are attracted to it.

6. (a) What would happen if you charged a balloon by rubbing it against your hair and then brought it near another balloon that is neutral? Explain. As a result, the rubber balloon will attract the electrons from your hair, creating an electronegative state that will cause it to adhere to the hair for a brief period of time. The negative charge on a balloon will be attracted to the positive charge on a neutral balloon if the negatively charged balloon is brought close to the neutral balloon. This will result in the electrons on the neutral balloon being pushed aside. (b) What would happen if the charged balloon were allowed to touch the neutral balloon? Explain. Excess electrons on the balloon will be transferred to the neutral balloon so that there is an equal number of electrons on both balloons, since electrons will move from the more negative object to the less negative one. 492-495 Q. 1,2,5 1. What precautions should you take before working with electronic equipment? Explain why. The accumulation of excess electrons while moving can transfer to neutral materials in a laboratory or damage electronic equipment, which can result in fluctuations in current and the discharge can be detrimental to the patient. 2. Suppose that you took off your sweater and noticed that your hair was standing up. Using six electrons as an example, and assuming that the electrons are transferred from the sweater to your hair, draw a series of diagrams showing how the excess electrons in your hair could be discharged. (a) to your neutral hand: (b) to the neutral ground:

5. Lightning sometimes happens between clouds. Suggest a possible way that a discharge can occur between clouds. The charge of one cloud, from which the discharge typically originates, propagates within the cloud formation and reaches the nearby cloud which has a different electrical potential. 472-477 Q.1-6 1. Consider the following pairs of materials. Using the electrostatic series, determine the charge that each material will gain when the two are rubbed together. (a) glass and silk In comparison to silk, glass is higher on the electrostatic series, causing it to lose electrons more rapidly. Silk will gain electrons from the glass. This will make the glass more positively charged and the silk more negatively charged. (b) ebonite and fur Ebonite will gain more electrons from the fur. This will make the fur more positive and the ebonite more negative. (c) human hair and a rubber balloon Human hair will lose more electrons to the rubber balloon than the balloon will to the hair, resulting in the hair being more positively charged and the balloon being more negatively charged. (d) amber and cotton Amber will gain more electrons from the cotton, becoming more negative as a result. The cotton will lose electrons and become more positive as a result. 2. Why do objects made from different materials develop an electric charge when rubbed together? What is this method of charging called? Use a diagram to illustrate your answer. There are atoms in the materials of one object that can gain more electrons than in the materials of another object. As a result, objects can be charged. In the event of rubbing objects of different materials together, this is known as charging by friction. An example would be the rubbing of a rubber balloon against a wool sweater. According to the electrostatic series, the rubber balloon tends to gain more electrons from the wooly sweater, making it more negatively charged.

An electron moves from a negatively charged object to a positively charged object. In this instance, rod Y is more electronegative than rod X. Their charges will continue to balance as long as they remain in contact. 6. Describe how electrons travel when a positively charged object is grounded. Upon reaching the neutral state, electrons travel up the positively charged object that is grounded. Electricity 4 Tues. May 31 Tasks: HOMEWORK SET 2 1. What is the difference between conductors and insulators? Give 2 examples of each. The main difference between conductors and insulators is that conductors are mainly composed of metals and insulators are non-metals. CONDUCTOR = METALS (Copper, silver, aluminum, mercury) INSULATORS = NON-METALS (wood, paper, plastic) 2. How could you reduce the static electricity in your house during winter? It is possible to reduce static electricity in my home by controlling humidity in the home, installing indoor plants, and taking super hot showers. 3. What is meant by discharging an object? When a charged object has all the excess electric charges removed and returns the object to neutral. 4. Why does the Earth not become charged when so many electrons are constantly flowing into it as various devices are grounded? The damp soil is a fairly good conductor and the Earth is so big that it effectively removes all excess charge from the object. 5. Why is there no static discharge at a gas station when the nozzle of the pump is brought up to the car's gas tank opening? Why is this necessary? In order to prevent the possibility of an explosion, all the parts of the gas pump and everything attached to it are carefully grounded. Once a charge is made at the nozzle, it is immediately conducted safely to the ground where it is released 5. A student builds a circuit that has a source of electrical energy, connecting wires, a switch, and a load. However, the circuit does not work. Suggest three possible reasons why the circuit does not work. A switch may be off, the power source may be depleted (for example, a dead battery), or the components may be improperly connected. 6. Which of the following parts of a circuit would be considered a load? Justify your answer by explaining your choice(s) ● Light ● Switch ● Motor ● Battery

It would be considered a load if the "light" and the "motor" were converting electrical energy into other forms of energy that could be useful. A light converts electrical energy into light and thermal energy, while a motor converts electrical energy into mechanical energy. A switch controls the flow of electrons in a circuit, so "switch" is incorrect. Battery is incorrect because it is an example of an energy source, which means that it supplies electrons to the circuit. 551-554 Q. 1,2,5,6 1. How many complete pathways are there for electrons to follow in each circuit shown in Figure 10? a. 1 complete pathway b. 4 complete pathways 2. Identify whether each circuit in Figure 11 is series or parallel. a. parallel - more than one path of electron flow b. series - one path of electron flow 5. Why are the outlets in homes never wired in series? What problems might this present? Normally, outlets in homes are not wired in series since if there were any damage to or disruption in the series, all of the outlets would lose power simultaneously. 6. A parallel connection of several lamps in a home allows you to control each lamp independently with switches. How is this possible? As electrons pass through parallel circuits, they can travel in multiple directions at the same time. The reason this scenario is possible is that each lamp has its own path of wires and is controlled by its own switch. As a result, even if one of the lamps is switched off, electrons can continue to flow through the circuit pathways that power the other lamps. 556-557 Q. 2,3 2. List two important things to remember when using an ammeter. - Make sure that the ammeter is set to the highest current setting in order to prevent damage to the device. - Avoid touching the tips of the ammeter leads when they are connected to a circuit, otherwise you will suffer an electric shock. 3. A student connected an ammeter as shown in Figure 3. Did the student connect the ammeter correctly? Explain. The student did not correctly connect the ammeter. A parallel connection was made between the ammeter and the load. In order to accurately measure the current flowing through a load, the ammeter must be connected in series with the load. 560-561 Q. 3,4 3. Give an example of how the potential difference would be measured in a circuit.

The resistance of a wire increases with its length since electrons have to pass through more material. (d) changing from a copper conductor to a silver conductor Reduced resistance: silver is a better conductor than copper, which means it resists the flow of electrons less. 7. An extension cord that you would use for a lamp is much thinner than an extension cord recommended for use with large appliances. If you plugged in a refrigerator using a lamp extension cord, the plastic coating of the cord could melt and perhaps start a fire. Why does this occur? How can this hazard be prevented? As a result, the lamp extension cord is of a small diameter and the refrigerator requires a large amount of power to function. A lamp extension cord with a small diameter resists the massive flow of electrons from the refrigerator to the outlet. In the cord, electrons frequently collide with the materials, which produces thermal energy and can melt the plastic coating. The lamp extension cord can be replaced with a larger diameter cord to prevent this. By providing more space for electrons to flow, a thicker cord reduces resistance and transforms less electrical energy into thermal energy (heat). HMWK: 568-570 Q. 9 9. Use Ohm’s law to explain why an electric shock applied on wet skin is more dangerous than the same electric shock on dry skin. According to Ohm's law, resistance is voltage divided by current. When electric shocks are applied to the skin, we are concerned about how much current will flow through the person. Consequently, Ohm's law can be rearranged to state that current is equal to voltage divided by resistance. Since both wet and dry skin receive the same shock, the voltage is the same. But the resistance is different. Dry skin conducts electricity better than wet skin, so wet skin has a lower resistance than dry skin. According to the equation I = V / R, a smaller resistance value will generate more current. A person's body receives a larger amount of current when they receive an electric shock on wet skin. HMWK: 571-575 Q. 2-6 2. Compare the total resistance of loads connected in series with those loads connected in parallel. Since electrons in series experience a greater resistance than electrons in parallel when they are exposed to more loads, they will experience more resistance. 3. Why is it a bad idea to connect too many devices in parallel to an energy source, such as a wall outlet? Due to the fact that the total current passing through all loads may be greater than the total current that is available at the source or in the circuit. 4. (a) What would happen to the voltage drop across each lamp if you kept adding lamps to a series circuit? As current flows from the source to the load, the voltage drops. As there is only one path on which the current flows, as the load increases, the current will decrease across each load and there will be more resistance. The battery can only provide a limited amount of potential energy for one load.

(b) What do you think you would observe in terms of the brightness of the lamps? From one load to another, the battery's potential energy decreases as it can only supply so much. As the lamps are dimmed, the first lamp will be the brightest. 5. The total resistance of the circuit in Figure 7 is 25 Ω. The voltage drop across the battery is 6.0 V. (a) Calculate the current in the circuit. G : R = 25, V = 6.0 R : I ? A : I = V/R S : I = 6.0 / 25 = 0.24 S : The current was 0.24 A. (b) Calculate the voltage drop across each lamp. G : V source = 6.0 V R : voltage drop across each lamp A : V load = V source / # of loads S : V load = V source / # of loads V load = 6.0 / 2 = 3 S : The potential difference across each lamp is 3 V. 6. A house has a lamp in every room. The circuit for the lamps is shown in Figure 8. The voltage drop across the energy source is 120 V. The total resistance is 10 Ω. (a) Calculate the current through each lamp. G : V source = 120 V R = 10Ω R : The current through each lamp (I load ) A : I source = V / R S : I source = 120 / 10 = 12 A. I load = 12 A / 4 = 3 A S : The current through each lamp is 3 A. (b) Calculate the voltage drop across each lamp. G : I source = 12 A R = 10Ω R : voltage drop across the energy source (Vsource) and across each lamp (Vload) A : V source = V load S : V source = (I source )(R) V source = 12 A (10 Ω) = 120 V S : The voltage across each lamp is 120 V. 3. Explain how EnerGuide labels are useful to consumers. The EnergyGuide labels provide consumers with information on how much electricity an appliance consumes over the course of a year. By comparing EnerGuide labels from similar appliances, consumers can purchase more energy-efficient products. 4. When purchasing an electrical device, what are the two financial costs you need to consider? Are there any environmental considerations you would make? Explain your reasoning.