The rechargeable batteries for a laptop computer need a muchsmaller voltage than

Question

The rechargeable batteries for a laptop computer need a muchsmaller voltage than what a wall socket provides. Therefore, atransformer is plugged into the wall socket and produces thenecessary voltage for charging the batteries. The batteries arerated at 9.0 V, and a current of 262 mA isused to charge them. The wall socket provides a voltage of 120V.
(a) Determine the turns ratio of thetransformer.
Ns Np = Enter anumber. 1

(b) What is the current coming from the wall socket?
Ip = Enter anumber. 23---Select---AWCVOhm

(c) Find the average power delivered by the wall socket and theaverage power sent to the batteries.
Pp = Enter anumber. 45---Select---CAOhmVW
Ps = Enter anumber. 67---Select---OhmAVCW (a) Determine the turns ratio of thetransformer.
Ns Np = Enter anumber. 1

(b) What is the current coming from the wall socket?
Ip = Enter anumber. 23---Select---AWCVOhm

(c) Find the average power delivered by the wall socket and theaverage power sent to the batteries.
Pp = Enter anumber. 45---Select---CAOhmVW
Ps = Enter anumber. 67---Select---OhmAVCW Ns Np = Enter anumber. Enter anumber. Enter anumber. Enter anumber. Ns Np

Explanation / Answer

   Since efficiency of transformer is notgiven, i assume that the tranformer is ideal.    For an ideal transformer    inputpower   =   output power    VS /VP   =   NS /NP   =   IP /IS    a.   NS /NP   =   VS /VP                         =   9.0/ 120                         =   3/ 40                         =   0.075                         =   9.0/ 120                         =   3/ 40                         =   0.075    b.   IP /IS   =   VS /VP      Current from the wallsocket   IP                =   0.075* IS                                                          =   0.075* 262 mA                                                          =   19.65   mA                                                          =   0.075* 262 mA                                                          =   19.65   mA    c.   Power delivered by wallsocket   PP   =   VP* IP                                                                   =   120* 19.65 * 10-3                                                                   =   2.358   W          Powersupplied to thebattery   PS   =   VS* IS                                                                =   9.0* 262 * 10-3                                                                =   2.358   W                                                                =   2.358   W

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