- The motor effect is sometimes demonstrated using the apparatus shown. A current flows through a wire 'swing. The swing hangs in a magnetic field. When the current is switched on, the swing is pushed out of the field.
-copper 'swing'
steel support rods
to power supply
a What will happen if the connections to the power supply are reversed?
b What will happen if the magnetic field is reversed?

when a device is used in a circuit in which the voltage is 81 v, the current flowing through the device is 3 a. what is the resistance of the device?

a. 27 ω

b. 40.5 a

c. 243 ω

d. 243 a

the correct answer is a. 27

answer: 2×10^-2kg

explanation: density= mass per volume

vol=mass/density

converting to s.i units we have;

3÷1000kg = 0.003

1.5÷100m = 0.15

0.003/0.15 = 0.02kg

the temperature in kelvin of 2.0 dm3 of an ideal gas is doubled and its pressure is increased by a factor of four. what is the final volume of the gas