If you dont mind splodey light bulb.
Technically speaking a bulb and a lamp are the same thing. You can use a 60 watt bulb in a fixture calling for a 40 watt bulb but I wouldn't. The lighting fixture may get to hot, melt and start a fire.
What may happen is the 7W bulb may burn out quickly because of the dryer heat. I suppose worse case might be an exploding 7W bulb that would ignite lint and cause a dryer fire. You should always use what is recommended by the manufacturer.
Any replacement bulb, LED or not, can be used, so long as the voltage specs are respected and that the bulb's contacts are of the same type.
you can always less less wattage. for safety, never use more wattage recommended due to fire hazard.
If the socket threads of the lamp are the same then yes the bulbs can be interchanged. The 5 watt bulb will glow brighter than the 4 watt bulb. If by a 4 watt light you mean a 4 watt fixture, then it is not recommended to place a larger wattage lamp in a fixture that is rated by the manufacturer at a specific operating wattage
A 75 bulb will use more electricity.
Yes.
No, you can not use a 150 watt high pressure sodium bulb with a 70 watt ballast.
The highest watt headlight bulb you can use in a 2000 Mazda 323 is 65 watts. Most vehicles use a 55 watt bulb.
A 40 watt bulb is dimmer than a 100 watt bulb.
no because it would blow up because the socket would draw 13 watt not 9 watt
That shouldn't be an issue refer to watts law: P / V x A Power Volts Amps