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Terms in this set (34)
List the three subatomic particles and describe their location and charge.
Neutrons: in the nucleus, have a neutral charge.
Protons: in the nucleus, have a positive charge.
Electrons: circulate around the atom, have a negative charge.
What type of charge moves through a circuit?
A negative charge moves through a circuit (negative). This is called an electric current.
Define insulator and provide two examples.
In an insulator, the electrons don't move easily. Insulators have a hold on electrostatic charge. Many are non-metals (rubber, plastic).
Define conductor and provide two examples.
In a conductor, the electrons move easily. Conductors don't have a hold on electrostatic charge. Many are metals (copper, iron).
Why don't you get shocked when putting plastic in an outlet?
Because plastic is an insulator. Electrons don't transfer through plastic.
Define static electricity and static discharge.
Static electricity is an electric charge that tends to stay on the surface of an object. It is the build-up of excess charge. It occurs when electrons discharge.
Static discharge is the release of static electricity when two objects come in contact.
Non-metal in which electrons can move fairly well (silicon).
Describe the electric field of charged objects.
Charged objects attract oppositely charged objects, and repel objects with the same charge.
Provide an example of how static can affect our everyday lives.
When we're doing laundry. Clothing that we put in the dryer can be of a variety of materials. Some have a stronger hold on electrons than others. A clothes dryer generates static charges on the materials while they rotate in the dryer (charging by friction).
What is charging by friction?
Charging by friction occurs when two objects of different materials rub together. One of them has a stronger attraction for electrons. This material gains electrons, and the other loses electrons.
A wool sweater is pulled over a cotton shirt and they rub together. Identify the charge that each material receives, how you know they will receive this charge, what type of charging has occurred, and how the materials will behave near one another after charging has occurred.
This is charging by friction. Since the cotton has a stronger hold on electrons, it will become negatively charged. The wool sweater loses electrons, so it becomes positively charged. I know this because of the electrostatic series. The materials will attract after charging since they are of opposite charges.
A negatively charged ebonite rod is brought close to, but does not touch, a neutral pith ball. What is the charge of each object and the change in their charge? Do they objects attract or repel? Describe the movement of electrons.
The ebonite rod is negatively charged. The pith ball is neutral. The rod exerts an attractive force on the pith ball, and induces the electrons of the pith ball to move to the side near the ebonite rod (induced charge separation).
A positively charged glass rod approaches and touches a neutral pith ball. What is the charge of each object and the change in their charge? Do the objects attract or repel? Describe the movement of electrons.
The glass rod is positively charged. The pith ball is neutral. The objects initially attract. The electrons from the pith ball transfer to the glass rod. Both objects end up positively charged.
A negatively charged rubber balloon is brought close to, but does not touch, a negatively charged pith ball. What is the charge of each object and the change in their charge? Do they objects attract or repel? Describe the movement of electrons.
The rubber balloon is negatively charged. The pith ball is negatively charged. The objects repel each other. There is no change in their charge. The electrons in both objects move away from the other object.
Describe what happens when a charged object comes close to, but does not touch, a neutral object. What is this process called? When the charged object moves away, what happens?
This process is called charging by induction. When these objects come close, but don't touch, they attract. The electrons of the neutral object move. If the charged object is negative, the electrons of the neutral object move away. If the charges object is positive, the electrons of the neutral object move towards the charged object. When the charged object moves away, the electrons will spread out again.
A negatively charged rod makes contact with a neutral object. Describe what will happen to the object. Discuss the movement of charges.
The objects attract. The electrons from the rod transfer to the neutral object. Both objects become negative.
Define current electricity.
Flow of electrons.
Three required components for a circuit?
Conducting path, load, power source.
State Ohm's law using words and in the form of an equation. What are the three math equations?
Georg Ohm found that the ratio of potential difference to current is a constant called resistance. R= V/I V=IR I=V/R
A flashlight powered by a 6V battery draws a current of 2A. What is the resistance of the bulb? Express your answer to one decimal place.
V= 6.0V R=V/I Therefore, the
I= 2.0A R = 6.0V/2.0A resistance of the
R=? R= 3.0 ohms bulb is 3.0 ohms.
A hair dryer has a resistance of 15 ohms. What current will it draw if it is powered by a 120V source? Express your answer to one decimal place.
V= 120.0V R= 15 ohms I=?
I= V/R I= 120.0V/15.0 ohms I= 8.0A
Therefore, the hair dryer draws 8.0A of current.
What instrument is used to measure current? How is it connected to measure the current in a circuit?
The instrument used to measure current in a circuit is the ammeter. It is connected in series with a device to measure the current.
What instrument is used to measure voltage? How is it connected to measure the voltage in a circuit?
The instrument used to measure voltage in a circuit is the voltmeter. It is connected in parallel with a device to measure its voltage.
What does it mean for two loads to be connected in series? What does it mean for them to be connected in parallel? Use diagrams to support your answer.
Series: if one stops working, so does the other, smaller voltage
Parallel: if one stops working, the other doesn't, same original voltage
Explain the difference between a wet cell and a dry cell. Is there any advantage to either?
Dry cell: cell with an electrolyte that is a paste (alkaline). Safer to use. Portable.
Wet cell: cell with a liquid electrolyte (solution of sulphuric acid) however this can cause an injury if contacted with skin. Generates more power.
They conduct charge between two electrodes.
Explain the difference between a primary and secondary cell. Identify any advantages/disadvantages of either one.
Primary: can only be used once. less expensive
Secondary: can be recharged. During recharging, chemical reaction in the cell is reversed. environmental hazard
When glass and silk are rubbed together:
electrons are transferred from the glass to the silk
Pith balls P, Q, and R are charged by contact. P and Q then repel each other. P and R attract.
P is negative. Q is negative. R is positive.
The potential difference in an operating circuit is doubled, and the resistance is halved. What change takes place in the current.
Why is cleaning sunglasses with a cloth on a hot, dry day not a good way to clean them?
Glass is at the top of the series. Positive charge on the glass. Attracts dust particles.
A parallel circuit is used to illuminate bulbs in a mirror. Why would a resistor be in series with each bulb? If one bulb burned out, what change would occur in the brightness of the other three bulbs?
A resistor would be in series with each bulb to slow down the current. The brightness wouldn't change since it's a parallel circuit.
A friend complains that she experiences a small shock after using a telephone. She wonders if it has an electrical fault. You know that your friend often places the telephone handset on one of her shoulders while she talks. What is the likely reason for the shock?
The friction between the telephone and the girl's clothing/hair causes her to get shocked. Discharging when she touches something afterwards (conductor).
Suppose that you have a part time job assembling electronic components at a factory. The electronic components arrive at your metal table after sliding through a plastic delivery tube. Some of the components you assemble do not work properly, and the manager thinks that you are responsible for this. Could the parts be faulty before you assemble them? Explain your reasoning. What suggestions would you make to solve the problem?
Plastic around the components causes static electricity. The components are charged, and when they touch the metal table, they discharge. There can be too much static electricity that fries the components.
The heating element in a toaster is a metal wire. What electrical properties do you expect that the wire has? What other properties are important in this type of application?
Wire is a conductor with high resistance. When the resistance is higher, the electric current coming out is lower and other forms of energy are produced (heat, light).
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