ame: Exam 1--PHYS 202--S12 Multiple Choice Identify the choice that best completes the statement or answers the question 1 Which of these statements is true about charging by induction? a it can only occur with protons c it can not be done to conductors b it causes a bigger charge than charge by conduction d it does not require contact between two charged objects 2 Look at this kid What is her problem? a the back of her head is positively charged c she has an excess of negative charges in her hair b the day is really, really humid d all of the negative charges on her head have moved to the ends of her hair 3 A charged particle sits in an electric field as shown here If the particle moves in the direction of dashed line (to the left), what is the charge of the particle? a positive c neutrally charged b negative d You must know the magnitude of the E-field to know the sign of the charge 1
4 The following figure shows equipotential lines for a configuration of charges Which charge has the greater magnitude? a the positive charge c both have the same magnitude b the negative charge d there is not enough information 5 The following is a plot of potential (V) versus position (x) You release a proton at the point x=a What will the particle do? a remain stationary c go to the left b go to the right d oscillate back and forth 2
6 What is the equivalent capacitance of this circuit? a 12 µf c 06 µf b 5 µf d 05 µf 7 What is the potential and electric field at the point P, which is in the center of this square? a E 0, V=0 c E=0, V=0 b E 0, V 0 d E=0, V 0 3
8 What is the voltage across C 1, the 2 µf capacitor? a 12 V c 6 V b 3 V d 4 V 9 You charge a capacitor with a battery of 10 V Then you remove the battery, so the charge remains constant Then you double the distance between the plates of the capacitor What is the new voltage across the capacitor? a 10 V c 100 V b 5 V d 20 V 10 What is the primary purpose of a capacitor? a to create a current c to complete a circuit b to store electrical energy d to create a potential difference 11 You wish to measure the potential difference across a resistor How do you hook up the device? a in series with the resistor c replace the resistor with the device b in parallel with the resistor d you can t measure the potential difference across a resistor 12 Which has a bigger resistance, a hair dryer (1000 W) or a light bulb (100 W)? a not enough info to tell c hair dryer b both the same d light bulb 4
13 Consider this circuit What is the current through the resistor? a 12 A c 48 A b 016 A d 008 A 14 The rate for electricity charged by Entergy is $005 per kilowatt-hour How much does it cost you to run your 1000 W electric heater for 2 hours? a $4 c $100 b $040 d $010 15 Which of these best describes an ammeter? a it measures voltage c it is hooked up in parallel with a resistor b it has a very small resistance d it has a very high power rating 5
Problem 16 (20 pts) a) What is the electric field in vector notation at the point ( 00 i + 20 j+10 k) meters if the electric potential is given by V=3xz 2y 2 + 4x 2 yz, where V is in volts and x, y, and z are in meters? What is the magnitude and direction of the force on a +2 C charge located at this position? 6
17 (10 pts) Consider these charged at the vertices of a right triangle What are the magnitude and direction of the force acting on particle 2, which has a charge of 2 10 4 C? 7
18 (15 pts) Consider this configuration of charges: a) What is the potential at the location of q 2, the +1µC charge? b) What is the total work required to assemble the charges? 8
19 (25 pts) Find the equivalent capacitance and the voltage and charge for each capacitor V 1 = Q 1 = V 2 = Q 2 = V 3 = Q 3 = V 4 = Q 4 = V 5 = Q 5 = V 6 = Q 6 = V 7 = Q 7 = C eq = 9
ID: A Exam 1--PHYS 202--S12 Answer Section MULTIPLE CHOICE 1 ANS: D PTS: 1 2 ANS: C PTS: 1 3 ANS: B PTS: 1 4 ANS: A PTS: 1 5 ANS: C PTS: 1 6 ANS: B PTS: 1 7 ANS: B PTS: 1 8 ANS: C PTS: 1 9 ANS: D PTS: 1 10 ANS: B PTS: 1 11 ANS: B PTS: 1 12 ANS: D PTS: 1 13 ANS: A PTS: 1 14 ANS: D PTS: 1 15 ANS: B PTS: 1 PROBLEM 16 ANS: PTS: 1 17 ANS: PTS: 1 18 ANS: PTS: 1 19 ANS: PTS: 1 1