Question 5

Question 5 A flat battery is charged at 12V with 4A for 12 hours after which time it is fully charged. The battery is then used to deliver 20A at 15V for 1.5 hours and then 16A at 12V for 25minutes after which time it is fully discharged. a)    Calculate the energy used to charge the battery          Power = volts x current= Energy = power/time 48/12 4000W  

 b)    The energy released by the battery during the two dischargesPower = volts x currentEnergy = power/ time 300/1.5200W192/0.25768Wc) The efficiency of the battery to two significant figures efficiency = output  x 100               968     x 100                            input                            400024% 

Question 5 A 100mm conductor has a current of 16.7A flowing through it. The conductor is placed in a circular magnetic field whose radius is 52mm. A flux of 58mWb is concentrated in the circular magnetic field a)    Calculate the flux density of the magnetic field    B=iu/A Step one: put the figures into the equation- we know B is the flux density IU is the Flux and A is the area- (we have to find out the area using the radius) B=  IU=58mWB A=(pi 52mm squared x 10-3) 8.49  Step two: work out the equation that we have put the figures in   =    58mWB                      8.49            = 6.83  B= Flux Density = 6.83T

a)    Calculate the force on the conductor To calculate the force on the conductor  we use the formula F= B x I x L We Know that: B = 6.83T                          I=   16.7A                          L = 100mm F = B x I x L F= 6.83 X 16.7 x 100(10-3)  = 11.4 N

  Question 5 A 25mm conductor is moved through a magnetic field at a speed of 15m/s. The magnetic field is made by concentrating 25mWb of magnetic flux in a rectangle whose dimensions are 20mm wide and 30mm high   a) Calculate the flux density of the magnetic field. B=iu/A A = Area =  600mm B= flux density Ui= magnetic flux = 25mWb   B= 600/25 = 0.04167x 1000( 10to the power of 3 because the area is in MM) B= 41.67T