The problems of physics that are given here can be solved using Ohms laws. As per the Ohms law, we can write
Resistance = Current/Voltage.
Now coming to the questions that are given.
1. In this question,
Current = 15 amperes
Voltage = 5 volts
Then
Resistance = 5/15
= 1/3
= 0.33 ohms
So the resistance of the tube will be 0.33 ohms
2. Given information's are noted below
Current = 2 amperes
Voltage = 120 volts
Resistance = 120/2
= 60 ohms
So 60 ohms of resistance is present in the bulb.
3. Given information's
Current = 250 watt
Voltage = 240 volts
Resistance = 250/240
= 25/24
= 1.04 ohms.
The radio will draw 1.04 ohms.