Which of the following statements about Earth’s magnetic field is true? a. The geographic North Pole of Earth and Earth’s magnetic north pole are at the same location.

b. The geographic South Pole of Earth and Earth’s magnetic north pole are relatively close to each other.

c. The north needle of a compass always points to the geographic North Pole of Earth.

d. The north needle of a compass points to Earth’s magnetic north pole.

Four point charges each having charge q are located at the corners of a square having sides of length a. find symbolic expressions for the following. (a) the total electric potential at the center of the square due to the four charges (use any variable or symbol stated above along with the following as necessary: ke.) vtotal= (b) the work required to bring a fifth charge p from infinity to the center of the square (use any variable or symbol stated above along with the following as necessary: w=