Spare 500g Iron Hooked Weight with Retractable Hook Subject_Astronomy Seven-junction copper-and-iron thermopile from four

Seven-junction copper-and-iron thermopile from four 130mm wires of each metal

Converts chemical energy to electrical through a zinc-copper-sulfate redox couple

Eight aluminum-shank tuning forks tuned to scientific pitch (C4 = 256Hz) and ranging from 5 9/16 to 7 1/8 inches

Thirty-five-component electronics kit extending the Electronics System 1 set with capacitors

Spare 500g Iron Hooked Weight with Retractable Hook Subject_Astronomy Seven-junction copper-and-iron thermopile from fourCast iron 500g mass carries a retractable hook for suspension from spring scales, pulleys, or beams, serving as a replacement piece for gravitational and force measurement setups.