Chapter 28 HW Solutions - PHYS 241 Ch. 28 Homework...

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

View Full Document Right Arrow Icon

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

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

Unformatted text preview: PHYS 241 Ch. 28 Homework Solutions 28.3. I DENTIFY : A moving charge creates a magnetic field. S ET U P : The magnetic field due to a moving charge is 2 sin 4 qv B r = . E XECUTE : Substituting numbers into the above equation gives (a) 7 19 7 2 6 2 sin 4 10 T m/A (1.6 10 C)(3.0 10 m/s)sin30 . 4 4 (2.00 10 m) qv B r --- = = B = 6.00 10 8 T, out of the paper, and it is the same at point B . (b) B = (1.00 10 7 T m/A)(1.60 10 19 C)(3.00 10 7 m/s)/(2.00 10 6 m) 2 B = 1.20 10 7 T, out of the page. (c) B = 0 T since sin(180) = 0. E VALUATE : Even at high speeds, these charges produce magnetic fields much less than the Earths magnetic field. 28.9.I DENTIFY : A current segment creates a magnetic field. S ET U P : The law of Biot and Savart gives 2 sin 4 Idl dB r = . E XECUTE : Applying the law of Biot and Savart gives (a) 7 2 4 10 T m/A (10.0 A)(0.00110 m) sin90 4 (0.0500 m) dB- = = 4.40 10 7 T, out of the paper. (b) The same as above, except 2 2 (5.00 cm) (14.0 cm) r = + and = arctan(5/14) = 19.65, giving dB = 1.67 10 8 T, out of the page. (c) dB = 0 since = 0. E VALUATE : This is a very small field, but it comes from a very small segment of current. 28.13. I DENTIFY : A current segment creates a magnetic field. S ET U P : The law of Biot and Savart gives 2 sin . 4 Idl dB r = Both fields are into the page, so their magnitudes add. E XECUTE : Applying the Biot and Savart law, where 2 2 1 2 (3.00 cm) (3.00 cm) r = + = 2.121 cm, we have 7 2 4 10 T m/A (28.0 A)(0.00200 m)sin 45.0 2 4 (0.02121 m) dB- = = 1.76 10 5 T, into the paper. E VALUATE : Even though the two wire segments are at right angles, the magnetic fields they create are in the same direction. 28.15. I DENTIFY : We can model the lightning bolt and the household current as very long current-carrying wires. S ET U P : The magnetic field produced by a long wire is 2 I B r = . E XECUTE : Substituting the numerical values gives (a) B = 7 (4 10 T m/A)(20,000 A) 2(5.0 m)- = 8 10 4 T (b) 7 (4 10 T m/A)(10 A) 2(0.050 m) B- = = 4.0 10 5 T. E VALUATE : The field from the lightning bolt is about 20 times as strong as the field from the household current. 28.21. I DENTIFY : 2 I B r = . The direction of B r is given by the right-hand rule in Section 20.7....
View Full Document

This note was uploaded on 03/18/2010 for the course PHYS 241 taught by Professor Milsom during the Fall '08 term at University of Arizona- Tucson.

Page1 / 5

Chapter 28 HW Solutions - PHYS 241 Ch. 28 Homework...

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