1. Electric fields around point charges Direction of E field is: Away from positive Toward negative

2. Fields around points of mass or charge a, b, c are points, Q is a charge

3. Example: What is the electric field 2.0 m to the right of a -21 μC charge? 47,000 N/C left

4. 6.54E6 N/C to the left What is the electric field at the x? (Magnitude and direction) AC +12.5  C -187  C 72.1 cm E A = kq A = 8.958E6 N/C to the left (away from +) r 2 E C = kq C = 2.423E6 N/C to the right (toward -) r 2 = - 8.958E6 N/C + 2.423E6 N/C = -6.54E6 N/C (Left) 11.2 cm x

5. Whiteboards: Field relative to points 11 | 2 | 323

6. 71.5 N/C to the left E for a point charge: E = kq r 2 k = 8.99x10 9 Nm 2 C -2, q = -1.45x10 -6 C, r = 13.5 m E = -71.5 N/C away from the charge, or to the left (toward the negative charge) Vera Similitude measures the electric field 13.5 m to the right of a - 1.45  C charge. What electric field in what direction?

7. +.11  C E for a point charge: E = kq r 2 k = 8.99x10 9 Nm 2 C -2, E = 2,120 N/C, r =.67 m q = 1.06x10 -7 C = +.11  C. It is a positive charge as the E-field is away from it Vesta Buhl measures an electric field of 2,120 N/C, 67 cm from a charge of unknown value. The electric field is away from the charge. What is the charge?

8. 1.1 x 10 7 m g for a point mass: g = Gm r 2 G = 6.67x10 -11 Nm 2 kg -2, g = 3.4 N/kg, m = 5.98x10 24 kg r = 10831137.03 m = 10.8 x 10 6 m (r e = 6.38 x 10 6 m) Amelia Rate measures a gravitational field of 3.4 N/kg. What distance is she from the center of the earth? (Me = 5.98 x 10 24 kg. )

9. 12  m E for a point charge: E = kq r 2 k = 8.99x10 9 Nm 2 C -2, E = 10 N/C, q = 1.602x10 -19 C r = 1.20008x10 -5 m = 12  m Tara Bull measures an electric field of 10. N/C what distance from an electron?