A child staying in a coastal region tests the drinking water and also the seawater with his tester. He finds that the compass needle deflects more in the case of seawater. Can you explain the reason?

Drinking water is chemically treated and purified by removing various impurities and salts from it. While the sea water contains lots of mineral salts. Therefore, sea water produce more ions (more electric charges) as compared to drinking water and the child sees more deflection in magnetic needle in case of sea water.

https://www.tiwariacademy.com/ncert-solutions/class-8/science/chapter-14/