How to make an electric motor

Warn­ing! Only un­der adult su­per­vi­sion.

Equip­ment

• bat­tery pack with bat­ter­ies and croc­o­dile clips;
• cop­per wire;
• sand­pa­per;
• wood­en stick;
• neodymi­um mag­net.

Step-by-step in­struc­tions

Wind a cop­per wire tight­ly around a bat­tery sev­er­al times. Wrap the free ends of the wire around the re­sult­ing coil sev­er­al times to fix the wires to­geth­er. Us­ing sand­pa­per, strip the in­su­la­tion from only one side of each free end of the wire. Break off two small pieces from a wood­en stick and in­sert them be­tween the bat­ter­ies. Fix the croc­o­dile clips on the pieces of wood. Set a neodymi­um mag­net on top of the bat­ter­ies. Place the ends of the loop on the croc­o­dile clips and tap the coil gen­tly – it will start to ro­tate, there­by start­ing the en­gine!

Sci­en­tif­ic de­scrip­tion

When the stripped sec­tion of the wire comes into con­tact with the croc­o­dile clips, this cre­ates a closed cir­cuit, through which cur­rent be­gins to flow. The loop ro­tates, try­ing to as­sume a cer­tain po­si­tion due to its in­ter­ac­tion with the field of the per­ma­nent mag­net. Strip­ping the ends of the wire only on one side pre­vents the loop from tak­ing the de­sired po­si­tion: when the in­su­lat­ed sec­tion comes into con­tact with the “croc­o­diles,” the cir­cuit opens, and the mag­net­ic field ceas­es to act on the wire. The loop con­tin­ues to ro­tate due to in­er­tia, over­shoot­ing its “com­fort­able” po­si­tion, and its stripped sec­tions once again touch the croc­o­dile clips, clos­ing the cir­cuit again. Thus, rev­o­lu­tion af­ter rev­o­lu­tion, the en­gine con­tin­ues to spin.

You can get these and oth­er ex­per­i­ments in the MEL Physics sub­scrip­tion!