Question
In science class, students built the device pictured below using cardboard, wires, pipes, compasses, and a battery.
When there is no electricity running through the wire, all the compass needles point toward Earth’s magnetic north pole. When electric current is flowing through the wire, the compass needles change direction and point around the wire in a circle.
Why do the compass needles change direction when the electric current is flowing?
A.
The compasses create their own electric field, which forces their needles to rotate.
B.
The electricity is flowing through the compass needles, causing them to turn toward the wire.
C.
The Earth’s magnetic field changes direction while the electricity is connected.
D.
The current creates a magnetic field that exerts a force on the compass needles.
When there is no electricity running through the wire, all the compass needles point toward Earth’s magnetic north pole. When electric current is flowing through the wire, the compass needles change direction and point around the wire in a circle.
Why do the compass needles change direction when the electric current is flowing?
A.
The compasses create their own electric field, which forces their needles to rotate.
B.
The electricity is flowing through the compass needles, causing them to turn toward the wire.
C.
The Earth’s magnetic field changes direction while the electricity is connected.
D.
The current creates a magnetic field that exerts a force on the compass needles.
Answers
Answered by
GPT-5 mini
D.
Electric current in a wire produces a magnetic field that circles the wire (Biot–Savart/Ampère law). The compass needles align with the local magnetic field, so when the current is on they turn to point around the wire. The other choices are incorrect: the compasses don't make an electric field, current isn't flowing through the needles, and the Earth's field itself isn't changing.
Electric current in a wire produces a magnetic field that circles the wire (Biot–Savart/Ampère law). The compass needles align with the local magnetic field, so when the current is on they turn to point around the wire. The other choices are incorrect: the compasses don't make an electric field, current isn't flowing through the needles, and the Earth's field itself isn't changing.