Điện trường xoáy có nguồn gốc như thế nào?

1.what is where an object is located 2. what is how fast an objects speed is changing 3. what is how fast an object is moving

On a day when the barometer reads 75.23 cm, a reaction vessel holds 250 ml of ideal gas at 20 celsius. an oil manometer ( ρ= 810 kg/m^3) reads the pressure in the vessel to be 41 cm of oil and below atmospheric pressure. what volume will the gas occupy under s.t.p.?

What is special about a dc circuit ?