When a thicker wire of the same material and length is used in a circuit, the ammeter reading is expected to decrease. This is because the thicker wire has a lower electrical resistance compared to a thinner wire of the same material and length. According to Ohm’s Law (V = I * R), where V is voltage, I is current, and R is resistance, the current (I) is inversely proportional to the resistance (R). With a lower resistance in the thicker wire, the current can flow more easily, resulting in an increase in current flow. Therefore, the ammeter reading will show a higher value when a thicker wire is used in the circuit compared to a thinner wire under the same conditions.