{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

# img058 - 96W V1.5 1008 PHY2054 Spring 2008 Prof P Kurnar...

This preview shows page 1. Sign up to view the full content.

This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 96W! V1.5 1008 PHY2054 Spring 2008 Prof. P. Kurnar Prof. P. Avery March 5. 2008 Exam 2 Solutions 1. Two cylindrical resistors are made of the same material and have the same resistance. The resistors, R1 and R2, have different radii, n and r;, and different lengths, L1 and L 2. Which of the following relative values for radii and lengths would result in equal resistances? @2n=rzand4L1=Lz )2r1=r2and L]: 21.2 (3) r1=r2and 4L1=L2 (4) r1=r2 and L1: 2L2 (5) none of these The resistance is given by R = pL /A , where p is the resistivity, L is the length and A is the cross sectional area. T 0 keep R unchanged, the ratio of L to A must be unchanged. Since A = 717'}, If r is doubled then L must be multiplied by 4. Only the answer (1) works. 2. If a 9.0-V battery with internal resistance 0.2 Q and an 18 Q resistor are connected together, what is the amount of electrical energy (in I) transformed to heat per coulomb of charge that ﬂows through the circuit? ® 9.0 (2) 3.0 (3) 0.50 (4) 72 (5) 4.5 The amount of heat released is PAt, where P = Vi. The total amount of charge is q = iAt. Thus the amount of heat energy released per coulomb of charge is PA! / iAt = P/i = V = 9V. M "e W’ . ~ ,,. , 7 , ...
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online