An electrician compares a cold ohmmeter reading of an incandescent lamp with the resistance worked out from its running voltage and current. How do the two values compare?

1. 1The running value is much higher, because the filament resistance rises as it heats.
2. 2The running value is much lower, because the filament resistance falls as it heats.
3. 3The two values are the same, because a filament is a linear resistor.
4. 4The running value is slightly lower, because the supply voltage drops when the lamp is on.