Problem 1 . A water droplet of radius 0.015 mm remains hanging stationary in the air. If the electric field of Earth is 100 N/C, how many excess electrons must the water droplet have? In which direction the electric field of Earth must be directed for that problem to make any sense? Problem 2. An electric dipole is formed from two charges, +/-q, spaced 1 cm apart. The dipole is centered at the origin, oriented along the y-axis. The electric field strength at the point (x,y)=(0cm, 10cm) is 360 N/C. What is the charge q? What is the electric field strength at the point (x,y)=(10cm, 0cm)? Problem 3 : Two 10-cm charged disks face each other, 20 cm apart. The left disk is charged to -50 nC and the right disk is charged to 50 nC. What is the electric field (both magnitude and direction) at the midpoint between the disks? What would be the force (again, magnitude and direction) on a -1 nC test charge placed at the midpoint? .
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