The image shows that an electromagnet made with a 1.5-volt battery (on the left). how would the strength of an electromagnet be affected if you replaced its 1.5-volt battery with a 9-volt battery (shown on the right) while using the same nail and coil?
a.
the magnetic field strength would increase.
b.
the magnetic field strength would decrease.
c.
the change would not affect the magnetic field.
d.
the magnetic field would change direction more frequently.

A.  The magnetic field strength would increase.

Explanation:

From ohm's law:

I ∝ V

When, voltage increases, current increases.

And in an electromagnet, strength of magnetic field increases with increase in current (I) and number of coil (n).

B = μ n I

Thus, when battery is changed, the magnetic field strength would increase because amount of current flowing in the conducting coiled wire.

A. The magnetic field strength would increase.

Explanation: I did the test

real, smaller and upside-down.   so the answer should be b.

measuring things 1 litre of water