Spin It: the DC Motor

Why it matters

Every fan, drill, toy car and lift shares one moving idea. And the idea isn't the coil or the magnets — it's a copper ring, sawn in half.

The idea in plain words

Anatomy of every motor you own. Tap the parts.

coil + field magnets + split-ring commutator + brushes

How do you make a DC motor spin FASTER?

Any of the three — exactly the electromagnet's knobs again

• the mover: armature coil — the current-carrying loop that feels the F = BIl push on each side
• the trick: split ring — two half-rings that swap contacts each half turn — reversing the coil current right on time
• the connection: brushes — carbon contacts that press on the spinning ring, feeding it current
• the conversion: energy — electrical → mechanical (a generator is this film played backwards)
• More current, stronger magnets, more turns on the coil
• (Each raises the BIl force on the sides)

Predict first

A coil in a field, fed through UNBROKEN slip rings, will…

After half a turn the same current now torques it BACKWARD. The split-ring commutator flips the current every half turn so the push always says 'keep going'.

• rock a half-turn and stall — the torque reverses on it — correct
• spin continuously
• not move at all

What you do

Assemble the motor. Try slip rings first — watch the stall — then fit the split ring.

Check yourself

The split ring's job is to…

Timed reversal keeps the torque one-directional — remove it and you built a rocking chair.

A DC motor converts…

Motor: current in, spin out. Generator: spin in, current out — same machine, opposite bookkeeping.

To reverse a DC motor's direction of rotation…

One flip reverses the FLHR force; two flips cancel — the same rule you proved on the jumping wire.

• reverse the coil's current every half rotation — correct
• reduce friction
• increase the voltage
• electrical energy to mechanical energy — correct
• mechanical to electrical
• chemical to electrical
• reverse the current OR the field (not both) — correct
• reverse both together
• increase the current