Hw Qn M5 Current Energy

CURRENT ELECTRICITY 1. A current of 4.0 mA flows through a resistor. Find the amount of charge that flow through the resistor in 30 s. [2] 2. 120 C of charge enters an ammeter every minute. What is the ammeter reading? [2] 3. Find the time taken for 80 C of charge to flow through a circuit carrying 2.5 A of current. [2] 4. Complete the table below to determine the potential difference, work done or charge. Potential difference Work done Charge 100 J 2C 12 V 10 C 8V 40 J 5. The potential difference across the lamp is 6 V. How much electrical energy is converted into light when Lamp a. A charge of 40 C passes through it? b. A current of 2 A flows through it for 2 minutes? 6V

6. Find the effective resistance of the resistors connected in the following arrangements. 3

3

6

3

3

7. A 4.0 kg mass of metal is dropped a distance 0.8 m onto a horizontal surface in order to test its hardness. a. When the mass has fallen through 0.8 m, how much gravitational potential energy has been transformed? [g=10ms2] b. How much kinetic energy does the mass possess just before it hits the horizontal surface? c. What is the velocity of the body just before hitting the horizontal surface? d. Assuming that 90% of the energy becomes thermal energy, how much thermal energy is produced when the body hits the horizontal surface? 8. The four tyres of a car are inflated to a gauge pressure of 200 kP. Each tyre has an area of 0.015 m 2 in contact with the road. e. What is the weight of the car? f. If the pressure in the tyres has been reduced to 150 kPa, what is the area of contact of each tyre with the road?

Yenny Tiga 2009