F= BIL

Emf and internal resistance 2 (y12)

y12 Thermistor 3

Electric Field Exam Questions (all of them in no particular order)

Alpha Particle Charged plates

E Field calc

E Field Bunsen Flame

Electron in E Field 3

Electron in E Field

Electron in E Field 2

Experiment with scales and rods

Force in Field

Internal Resistance of a cell

Internal Resistance

Q 1,2 & 3 Look up the answers in your text books.

Q4       Total R = 2 + 5.5

            I =  1.5 V/Total R

            Pd across cell = pd across external R = I(5.5) = 1.1V

Q5       emf = 1.5V

            Lost volts = (1.5 – 1.2) V

Internal r = lost volts/0.30A = 1.0 ohm

External R = 1.2V/0.30A = 4.0 ohm

Q6       lost volts = 100A (0.04 ohm) = 4V

            Only 8V across external circuit so bulbs are dim

Q7       I=V/R= 1.25V/25 ohm = 0.05A

            Internal r = lost volts/I = 0.25V/0.05A = 5 ohms

            Total R with 10 ohm = 10 + 5 =15

            I = E/R = 1.5/15 = 0.1A

            V across terminals= V across 10 ohm R = 0.1A(10 ohm) = 1V

Coulomb's Law Practical

Electric Power and Cost

1 (a)      P = VI               P power in W

                                    V p.d. in V       

                                    I current in A

3000 = 240 x I

I=3000/240 =12.5A

(b)      V = IR

240=12.5R

R = 240/12.5 = 19.2 Ω

(c)      3 kW = 3000 W = 3000 joules per second

Energy used in 1 min = 3000 x 60 = 180 000 J

2        8A       31.25Ω

3        Resistance depends upon temperature

4        1 641 600 J

5        4800J

6        6

7        2.083 kW

8        1920W 1687.5 W

9        .64m

10.     21.6p  19.1p

11      £1.16

12      0.54kWh

13      .42 kWh        .112p + 3.79p = 3.9p

14      4.46p            9.34p

Extra  50kW  0.072W