Concepts sheet Electrostatics Exam Give examples of charging by induction, conduction, and friction. Understand insulators vs. conductors. How do charged objects attract neutral objects? What is Coulomb’s Law? Draw electric field lines for a) a single negative point charge, b) a single positive point charge, c) two identical positive charges, d) two identical negative charges, e) one positive charge and one negative charge of the same magnitude, and f) a parallel-plate capacitor What is capacitance? What is a dielectric? Name two advantages of using a dielectric. Differentiate between electric potential (voltage) and electric potential energy. How is electric potential energy analogous to gravitational potential energy and spring potential energy? Understand the connections between at least one real-life topic and the parallel-plate capacitor model (either the plasma membrane that we went over in class or the topic you researched for your poster)

Equation sheet for exam

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Today’s Categories… Electric Fields Electric Force Voltage (Electric Potential) and PE Capacitors Methods of Charging Random

Electric Fields Electric Forces Voltage and PE Methods of Charging Capacitors Random $100 $100 $100 $100 $100 $100 $200 $200 $200 $200 $200 $200 $300 $300 $300 $300 $300 $300 $400 $400 $400 $400 $400 $400 $500 $500 $500 $500 $500 $500

Electric Fields - $100 Draw the electric field on a single positive point charge and a single negative point charge. Lines will point toward negative and away from positive Back to Board

Electric fields - $200 When the positively charged puck is released, it will Head straight for the goal Head toward the positive “plate” Head toward the negative ”plate” C Back to Board

Electric Fields - $300 If q is negative, what is the direction of the electric field at point P? To the left Back to Board

Electric Fields - $400 Which diagram best illustrates the electric field around two unlike charges? A. B. C. D. B Back to Board

Electric Fields - $500 R is a small test charge feeling the field generated by point charges P and Q. Determine Whether P and Q are positive, negative, or neutral Which direction R will move if it is negative P and Q are positive, R will move toward P Back to Board

Electric Force - $100 An electric force F exists between two charged spheres. If the quantity of charge on each sphere is doubled, the electric-force between the two spheres will be equal to F/2 2F 3F 4F D Back to Board

Electric Force- $200 Two charged objects are separated by a distance d. The first charge is larger in magnitude than  the second charge.       A)  The first charge exerts a larger force on the second charge.        B)  The second charge exerts a larger force on  the first charge.         C)  The charges exert forces on each other that are equal in magnitude  C Back to Board

Electric Force - $300 Two objects exert 90 N of electric force on each other when they are 3 m away from each other. When they are pulled 9 m away from each other, what is the new magnitude of the force on them? 10N Back to Board

Electric Force- $400 Two electrons are separated by a distance of 3.00E–6 meter. What are the magnitude and direction of the electrostatic forces each exerts on the other? A. 2.56E–17 N away from each other B. 7.67E–23 N away from each other C. 2.56E–17 N toward each other D. 7.67E–23 N toward each other A Back to Board

Electric Force- $500 Two balloons exert 0.005 N of force on each other and repel each other a distance of 20 cm. Calculate the charge on each balloon. 1.5 x 10-7 C Back to Board

Voltage and PE $100 The energy required to move one elementary charge through a potential difference of 5.0 volts is A. 8.0 J B. 8.0E–19 J C. 1.6E–19 J D. 5.0 J B Back to Board

Voltage and PE $200 Moving 2.5E–6 coulombs of charge from point A to point B in an electric field requires 6.3E–4 joules of work. The potential difference (voltage) between points A and B is approximately A. 1.6E–9 V B. 4.0E–3 V C. 2.5E2 V D. 1.0E14 V C Back to Board

Voltage and PE $300 Where would you move the positively charged puck to in order to decrease its potential energy? Up Down Right Left N/m

Voltage and PE $400 An electron placed in the center of this electric field would move A. Right B. Left C. Up D. Down right Back to Board

Voltage and PE $500 Suppose an electron in an old school TV picture tube is accelerated from rest through a potential difference ∆V = +5000 V. What is the change in potential energy of the electron? 8x 1016 J Back to Board

Methods of Charging- $100 What method of charging is Reuben using to charge the babies? friction Back to Board

Methods of Charging - $200 A negatively charged plastic tube is brought close to, but does not touch, a small piece of paper. If the tube and the paper are attracted to each other, the charge on the paper A. may be positive or neutral B. must be negative C. must be positive D. may be negative or neutral A Back to Board

Methods of Charging - $300 An originally neutral metal saw (conductive) is used to cut down an originally neutral tree (less conductive). Friction between them makes the tree positively charged Negatively charged Remain neutral b. Negatively charged Back to Board

Methods of Charging - $400 An electrically neutral object can be attracted by a positively charged object because A. like charges repel each other B. the net charge in a closed system varies C. the neutral body becomes charged by contact D. the charges on a neutral body can be redistributed D Back to Board

Methods of charging - $500 The diagram below shows two metal spheres charged to +1.0E-6 coulomb and +3.0E-6 coulomb, respectively, on insulating stands separated by a distance of 0.10 meter. The spheres are touched together and then returned to their original positions. What is the new charge on the spheres? 2 E-6 Back to Board

Capacitors - $100 Which of the following increases the capability of a capacitor to store charge? Choose all that apply. Decreasing the area of the plates Increasing voltage between plates Moving plates closer together Adding a dielectric Moving plates farther apart D Back to Board

Capacitors- $200 Which of the following is not an advantage of using a dielectric? It increases the capacitance It increases the charge stored It decreases the voltage It allows you to decrease the distance between the two plates without the two plates touching All of the above are advantages C Back to Board

Capacitors - $300 Which of the following increases the capability of a capacitor to store charge? Choose all that apply. Decreasing the area of the plates Increasing voltage between plates Moving plates closer together Adding a dielectric Moving plates farther apart D, C Back to Board

Capacitors - $400 Calculate A) the capacitance of a capacitor whose plates are 20 cm × 3.0 cm and are separated by a 1.0-mm gap and B) the charge on each plate if they’re hooked up to a 12-V battery. (Be careful with conversions!) 5.3 x 10-11 F, 6.4 x 10-10 C Back to Board

Capacitors- $500 Back to Board You have a capacitor you need to charge, which typically uses a 12V battery to charge. If you only had a AA (1.5V) battery on hand, how would you need to change the capacitor in order to store the same amount of charge? (Hint: first figure out the factor by which the capacitance should increase or decrease) Increase the area of the plate by a factor of 6 Decrease the distance between the plates by a factor of 8 Decrease the dielectric constant by a factor of 8 B Back to Board

Random $100 An object possessing an excess of 6.0E+6 electrons has a net charge of magnitude 5.5 x 10-24 C 9.6 x 10-13 C 2.7 x 10-27 C 3.8 x 10-13 C B Back to Board

Random $200 In the charging of a solid, charge transfer is accomplished by the displacement of A. both electrons and protons B. protons, only C. neither electrons nor protons D. electrons, only D Back to Board

Random $300 An electrically neutral object can be attracted by a positively charged object because A. like charges repel each other B. the net charge in a closed system varies C. the neutral body becomes charged by contact D. the charges on a neutral body can be redistributed D Back to Board

Random $400 A particle could have a charge of A. 0.8E–19 C B. 1.2E–19 C C. 3.2E–19 C D. 4.1E–19 C C Back to Board

Random $500 A rod is brought near an electroscope, and the leaves separate. What is the charge, if any, on the rod? No charge Positive charge Negative charge An unknown charge D Back to Board