A tungsten wire is 1.50 m long and has a diameter of 1.00 mm. At ...

[tuffie]

A tungsten wire is 1.50 m long and has a diameter of 1.00 mm. At 20C a current of 50 mA flows through this wire.
 
  The temperature coefficient of resistivity for this tungsten is 4.5  10-3/C, and its resistivity at 20C is 5.6  10-8   m.
  (a) What is the potential difference across the ends of this wire at 20C?
  (b) If the wire temperature increases by 100 C, what potential difference across its ends is now required to produce a current of 50 mA?

Question 2

A thallium source with a half-life of 3.7 years was certified at 10 kBq ten years ago. What is its activity now?
 
  A) 4.7 kBq
  B) 3.3 kBq
  C) 1.5 kBq
  D) 1.0 kBq

[ASDFGJLO]

Answer to Question 1

(a) 5.3 mV (b) 7.8 mV

Answer to Question 2

C

[tuffie]

Gracias!

[scottmt]

TYSM