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Chapter 2 Review Get out your notebooks and open up to your review. You must have it COMPLETED to stay and go over the answers!!! Reviewing Key Terms • 1. The attraction or repulsion between electric charges is called__________. – B. electric force (p. 36) • 2. The potential difference that causes charges to move in a circuit is called____. – D. voltage (p. 48) Checking Concepts • 6. Conduction is the process of charging an object with out touching it. – False: INDUCTION (p. 38-39) • 7. Electrical resistance is low in a good conductor. – True (p. 47) • 9. In a series circuit, all parts of the circuit are connected in a single path. – True (p. 64) • 11. Describe the three ways in which an object can become charged. – p. 38 – An object can become charged by friction, conduction, or by induction. • Friction-Electrons are rubbed off one object onto another object • Conduction- One charged object touches another and transfers charges • Induction- an electric field around a charged object attracts or repels electrons in another object 1 • 12. What units are used to measure voltage, current, and resistance. (KIDS DIDN’T HAVE TO DO, but they may want to write this down :) ) – – – – Voltage- volts Current- ampere (amp) Resistance- the ohm p. 61 • 13. Explain how the components of an electrochemical cell produce voltage. – An electrochemical cell consists of two different metals called electrodes immersed in an electrolyte. A voltage is produced when one electrode reacts with the electrolyte and becomes negatively charged and the other electrode reacts with the electrolyte and becomes positively charged. – p. 56 • 14. What is Ohm’s Law? – Resistance is equal to the voltage divided by the current. – p. 61 • 15. What would happen if the circuits in your school building were series circuits? Explain. – If one electric appliance or device in the building failed, all the others would stop working, too. The single path for the current in a series circuit would be broken. – p. 64 Thinking Critically • 18. Classifying: Identify each of the following statements as characteristic of series circuits, parallel circuits, or both: – p. 64-65 – A. Current= Voltage divided by Resistance • both – B. Total resistance increases as more light bulbs are added. • series – C. Total resistance decreases as more branches are added. • parallel – D. Current in each part of the circuit is the same. • series – E. A break in any part of the circuit will cause current to stop. • series 2 • 19.Is the electroscope shown below charged or uncharged? Explain. – Charged: the evidence is that the leaves are shown repelling each other, which means that the charge of both leaves is the same. – p. 40, figure 5 • 22. A toaster is plugged into a 120-volt socket. If it has a current of 0.25 amps in its coils, what is the resistance of the toaster? Show your work. – R=V/I; R= (120 V)/ (0.25 A)= 480 Ω – p. 61 • 24. Is the circuit in the illustration a series or parallel circuit? Explain. • 23. The voltage of a car battery is 12 volts. When the car is started, the battery produces a 40-amp current. How much power does it take to start the car? – P=V I; P= 12V x 40.0A= 480 W – p. 69 – Both. Bulbs 2 and 3 are in parallel with each other, and both are in series with bulb 1. • 25. Would the other bulbs continue to shine if you removed bulb 1? – No, they would go out because the circuit would be broken. Would they shine if you removed bulb 2 instead? Explain your reasoning. – Yes, they would be lit because the current has an alternate route. 3 From p. 56-57 • 26. Will any of the bulbs be light if you open the switch? Explain. – None of the bulbs would be lit if the switch were open because it would break the circuit and stop the current. • What type of energy is transferred from a battery to a wire? From a wire to a bulb? – From a battery to a wire, chemical energy is changed into electrical energy. – From a wire to a bulb, electrical energy is changed into heat or light energy. • As the energy sources (batteries) are added to a circuit, what happens to the voltage? – It increases. The amount of voltage in a circuit is equal to the sum of the voltage of the batteries in the circuit. 4