UnitExam3Bsolutions

UnitExam3Bsolutions - ID: B UCSD Physics 2B Answer Section...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
ID: B 5 UCSD Physics 2B Unit Exam 3B Current, Resistance, Circuits Answer Section MULTIPLE CHOICE 1. ANS: A when all resistors are identical R SER = NR = 3 × 15 Ω= 45 Ω TOP: SERIES 2. ANS: B R = ρ L A = s s 2 = Rs = 1320 Ω () 17.2 × 10 2 m Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ = 227 Ω• m TOP: RESISITIVITY 3. ANS: C The middle lamp is "shorted out" and therefore has no current through it since the potential difference across it is zero. At the same time, the total resistance of the circuit is lowered so more current flows through the remaining bulbs. You can also see this by recognizing the circuit as a voltage divider. When the middle bulb is shorted, the battery voltage is divided between only two remaining bulbs, so they are brighter than when the voltage was divided by 3. TOP: DEMO 4. ANS: A Each differential area element dA of a circle (cross section) is a ring of thickness dr and length (circumference) 2 π r . The area of this ring is the product, dA = 2 rdr I = J = Jr 2 0 R = 2 Kr 3 dr 0 R = 2 K R 4 4 = 1 2 3.14 12.2 A / m 4 Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ 16.6 × 2 m Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ 4 = 14.5 mA TOP: CURRENT DENSITY + INTEGRATION 5. ANS: B Resistance is directly proportional to length.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 4

UnitExam3Bsolutions - ID: B UCSD Physics 2B Answer Section...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online