8. The solar wind consists of particles, including protons, that flow outward fr

Question

8. The solar wind consists of particles, including protons, that flow outward from the Sun. Near the Earth, the density of protons in the solar wind is 8.72×10-6 protons/cm3, speeding through space at 475 km/s. What is the magnitude of the current density of protons near the Earth?

9. A resistor has a potential difference of 5.65 volts applied across it, and a current of 345 mA flows through it. What is its resistance?

10. You find a used battery and discover that it is no longer strong enough to power your CD player. Out of curiosity, you decide to find out what potential difference it actually supplies. You connect it to a 1.25 kO resistor and an ammeter (a device that measures current) and discover that the current through the circuit is 1.03 mA . What is the potential difference?

Explanation / Answer

8.
8.72*10^6 protons/cm^3 = 8.27*10^12 protons/m^3

each proton has a charge of (+1.6*10^-19C), so that is a charge density of:
(8.72*10^12 protons/m^3)(+1.6*10^-19C) = 1.3952*10^-6C/m^3

Imagine these charges as boxes with 1m on each side. If the particles are moving at 475 km/s or 475,000 m/s, then 475,000 of these boxes would pass a given point each second. So,

(475,000 m/s)*(1.3952*10^-6C/m^3) = 0.66272 A/m^2

9.

V = IR

5.65V = (345*10^-3A)R

R = 16.38

10.

V = IR

V = (1.03^10^-3A)(1.25*10^3) = 1.288V

Related Questions

Navigate

• Browse (All)
• Browse 8
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.