Sharks and related fish can sense the extremely weak electric fields emitted by their prey in the surrounding waters. These detectors, located in their noses and called ampullae, are so sensitive they can detect a voltage gradient of 1 ?V across1 cm of seawater.

How far apart would you have to place the poles of a 1.5 V battery to achieve the same electric field? (Choose one)

1) 6.7×10-9 m

2) 1.5×10-2 m

3) 1.5×10-6 m

4) 1.5×104 m