**Ohm's law**

**1. Calculate the current through the following resistors:**

**(a) 100 Ω connected to 240V (b) 4700 Ω connected to 24V**

**(c) 10kΩ connected to 3V (d) 2.5MΩ connected to 30V**

**2. What is the resistance of the following?**

**(a) a torch bulb that draws 0.25 A from a 12V supply**

**(b) an immersion heater that draws 10 A from a 240V supply**

**(c) a watch taking a current of 0.25 mA from a battery of 1.5 V**

**3. Under what conditions is Ohm's law obeyed?**

**4. Under what conditions is Ohm's law not obeyed?**

**5. What voltage is required to give a current :**

**(a) of 2 A through a resistor of 200 Ω?**

**(b) of 50 mA through a resistor of 1000 Ω?**

**(c) of 200 mA through a resistor of 300 kΩ?**