A mobile telephone is supplied by a Li-ion secondary battery whose capacity (in
ID: 2085114 • Letter: A
Question
A mobile telephone is supplied by a Li-ion secondary battery whose capacity (in the fresh state) is 1200 mAh. The technology used means that this capacity is practically unchanged regardless of the discharge current rate. Standby mode consumes 1.7 mA. Conversation mode consumes 65 mA in GSM operation and 220 mA in 3G operation. For each of these modes of operation, we shall take the consumption to be constant. What is the range (in hour/days) of such a telephone in GSM operation and then in 3G operation if it is in "conversation" mode for 5% of the total time? (5)Explanation / Answer
Standby mode:-
discharge current = 1.7 mA
Total capacity of Li-ion battery = 1200 mAh
No.of hours mobile telephone operates in standby mode is = 1200 / 1.7 = 705.88 hours
GSM mode:-
discharge current in GSM mode = 65 mA
No.of hours mobile telephone operates in GSM mode is = 1200 / 65 = 18.46 hours / day
5% of total time = 24*0.05= 1.2 hours
No.of days telephone operates in GSM mode is = 18.46/1.2 = 15.33 days @ 1.2 hours
3G mode:-
discharge current in 3G mode = 220 mA
No.of hours mobile telephone operates in 3G mode is = 1200 / 220 = 5.45 hours / day
5% of total time = 24*0.05 = 1.2 hours
No.of days telephone operates in GSM mode is = 5.45/1.2 = 4.54 days @ 1.2 hours
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