RI 14 Current of Electricity Tutorial

(c) W hat is its resistance under these operating conditions? (b) A t w hat rate is electrical energy dissipated in the bulb w hen it is operating at its rated voltage? (a) H ow m uch charge flows through the bu©¥b in 1 . 0 hour w hen it is operating at its rated cu©¥T ent? P 1 . A torch is rated as ' 2 . 5 V , 0 . 030 A T . S elf - P ractice w u e stio n s 5 12 . S tate the m axim um power theorem . 5 11 . H ow does the internal resistance of a battery affect its term ina©¥ p . d. A n d output pow eť ? resistor in term s of R ? If the circuit elem ent is a resistor of resistance R , w h a t is the electric power delivered to the passing through it, w hat is the electric power P delivered to or extracted from the circuit elem ent? F or an electric circuit elem ent w ith potential difference V be©¥w een its term ina©¥s and current !5 10 . 5 9 . S ketch the tem perature characteristic of a therm istor. sem iconductor diode and a filament ©¥am p . 5 8 . S ketch and exp©¥a©¥n the F V characteristics of a m etallic conductor at constant tem perature, a 5 7 . S tate O hm ' s Law . d]¨¤erence (p, d. ) ¡¤ 5 6 . U se energy consldera©¥©¥ons to distinguish between e©¥ectrom otlve lorce (e, m , r. ) and potential 5 5 . S tate the dellnltion of electrom otive force. 5 4 , State the dellnlt©¥on b r potentla©¥ dl¨¤erence be©¥ween Iwo pointa. 5 3 . State the equat©¥on re©¥allng current and dr¨¤ voloci©¥y . E xplain all ©¥y nbo©¥©¥ u©¥ed, 5 2 . Stale the equa©¥lon re©¥a©¥ing charge Q and cunen©¥ ©¥. 5 1. E xplain what ©¥©¥ m eant by an e©¥eclrlc current. S e©¥f - c heck Q uestions 1 4 pH Y S ©¥C S D E pA R T M E N T R A F F L E S IN S T ©¥T U T ©¥O N

. , inversely proportional to . N 88/I/13 D inversely proportional to x. C independent ofx. B proportiona©¥ ' to x. Aĉ ¡¤ proportiona©¥ to ©¬. d is . the case and the m eta©¥ tT he resistance betw een H H -«Ò¡¢ tthe diag ram . II m etal rodȘto a depth x as show n in : a cy ©¥ind rical m eta©¥ case Ą conducting liquid fil©¥sP 7 Ą conducting liquid fills 0 0 . 1 0 . 2 0 . 3 0 . 4 0 . Ś(b) W hat is the pow er dissipated at point 1 and point 2 ? V / V 0 . 01(a) W hat is the resistance at point 1 and point 2 7 O . :- l====l P 6 . A n electrical device has the V graph as show n. (resistivity of constantan - 4 . 吕 ¡¿ 1 0 7 Q m ) this wire w ould be needed to m ake a ' 1 2 V , 30 W heater lilam ent? (b) C alculate the resistance per m etre of constantan w ire of diam eter 0 . 35 m m . W hat length of than 5 . 0 V along ©¥ts length. W hat is the m inim um acceptable diam eter of thle cable? (a) A constanten w ire of length 1 5 m is to carry a curreń t of 2 5 A w ith a potent©¥al drop of no m oreP 5 . (b) W nat ©¥s the resistlvlty of the m ateria©¥ from w hich It ls m ade? (a) W nat ls the res©¥stance of thle conductor? current of 4 . 60 A w hen a p . d. o f 60 . 0 V le applied between lte endB . P 4 . A cylindrical conductor w ith a length of 2 . 00 m and a diam eter of 0 . 500 cm la found to carry a p3 . D lstlnguiah between resistance and resletlv©¥ty . 30 C . If the energy l©¥berated ©¥a 2 . 1 ¡¿ 1 0 " J , w nal ©¥a the p . d. ©¥nvolved? (b) ït is estim ated that the average quant©¥y of eleclrlc charge transported In a llghlen©¥ng ñ ash ©¥e 1 . 5 ¡¿ 1 0 " m once a year. E sl©¥m ate the average electric current along the orbH . the eurface of the E arth ©¥B 6 . 6 ¡¿ 1 0 ' C . T he E arth . R e v o lves around the S un at a distance of (a) T he E arth as a whole caM es negat©¥ve charge©¥. O r \ a day wtih nne weather, th e to ta l charge onP 2 . pH Y S ©¥C S D E pA R T M E N T R A F F L E S iN S TIT U T IO N

c P - ( R E p - \ k - h - P ť W hat js the ppwer input to the factory? connected to a faciory by cab©¥es of total re s i s tari Ę e R . p11 . A generator, w ith outpi©¥t pow er P and outpu¨© voltage {V is C a©¥cuïate the term inal p . d. o f the cell w hen m axim um pow er is delivered . vaïue? (b» W nat ¡¤ is the value of the external resistance if the pow er delivered is to have a m axim um (a» C alculate the pow er delivered to an external 2 . 5 Q resistor. A cell has e . m . f. 1 , 5 V and internal resistance 0 . 5 0 .P 10 . (b) W nat is the pow er dissipated in the cable? (a) W nat is the potential drop across the alum inum cables? diam eter of 8 . 25 m m , a re s istivity of 2 . 80 ¡¿ 1 0 - o O m and it carries a current of 1 2 5 A the p©¥ane. T he alum inum cab©¥es connecting the battery and the m otor has a length of 6 . 10 m , a For proper balance in som e sm al©¥ aircraft, the 12 , 0 V engine battery m ust be ©¥ocated in the tai©¥P 9 . D T he re8 ©¥s©¥ance of the reslslor equals that of the « lam enl ©¥am p w hen V - O ©¬V , C T he resistance of the fuam ent lam p ©¥s tw ice that of the res©¥stor at 1 . 0 V . B T he res©¥stance of the d©¥ode ©¥s conetant above 0 . 8 V . A The res©¥stance of the d©¥ode equals that of the fl©¥am ent ©¥arnl» at about 1 . 2 V . W n©¥ch statem ent ©¥8 comocť? pH Y 8 ©¥C 8 D E pA R T M E N T R A F F L E 8 IN 8 T IT U T IO N

4 , q ; ©© J - (resiótivi \ of copper- 8 9 6 0 kg m « , m a s s o f each copper atom ¡¤ 1 . 06 ¡¿ 1 0 - 2 s kg) one free electron, e s tim ate the drift velocity of the free electrons in the w ire. 侧ÙÍÙ³A copper w ire of diam eter 1 m m carries a current of 1 A . G iven that each copper atom contributes êÅ国ûöD 2 . [0 . 250 ¡¿ 1 0 3 C s ' 1 , 0 . 03 ¡¿ 1 0 3 C S - 1 , 9 ¡¿ 1 0 " s - ' ] unreliable. (d) B y considering the significant figures available, e x plain w hy your answers to (b) and (c) are that the charge on each positive particle is + 3 . 20 ¡¿ 1 ( r ' " C . the num ber of positively charged particles passing any point in the gas per second, g iv e n (b) the positive charge R ow ing past any point in the gas per second, (a) the negative charge f©¥ow ing past any point in the gas per second, C alculate negative particle is 1 . 6 0 . 1 ( r " C . particles passing any point in the gas per unit tim e is 1 . 56 ¡¿ 1 0 " s - 1 a n d the charge on each In this case, th e c o pper conductors to the gas cany a current of 0 . 28 m A . T he num ber of negative pressure conductor gas at low copper ʦ ìé ìòʦ ― ― ¡£ ¡£ ìé 吵 ìé flow ing in the opposite direction as show n below . In a gas, c o n duction occurs as a result of negative particles flow ing one w ay and positive particles [N gg/3/5 partiD 1 D iscussion Q uestions P H Y S IC S D E P A R T M E N T R A F F L E S ©¥N S T IT U T IO N

Ka) 1 . 62 - 1 . 6 3V (b) 0 . 38A J (b) E stim ate the new current f©¥ow ing through the cell If its em f is doubled. current In the circuit ©¥s 0 . 2 A . C alcu©¥ate the e. m . f of the cell. (a) T he resistors R and X are connected In serles w ith a cell of negligible interna©¥ resistance. T he V /V 0 he graph below show s the A V characteristics of two resistors R and X 0 , 2 - OA 0 . 6 uA Ï¡ ¡á ÷é ËÍ üÞ üÞ ï£ 园 ÞÌ 国 学 üÞ 国 与 国 国 ÙÍ ï£ ï£ ÙÍ ÙÍ ù½ 国 与 国 与 ÞÌ 国 ÙÍ ãý ÙÍ üÞ üÞ r ªê ¡á ÎÄ ÙÍ ÞÌ 国 üÞ 国 国 与 国 ù½ ÙÍ Ïê Ïê 与 园 ï£ ù½ 図 ठ园 ãý ÍØ ÙÍ 战 国 ì¹ ÚŠ׿ 4 ÙÍ üÞ 国 üÞ 国 国 üÞ üÞ üÞ 国 国 园 ÙÍ 国 üÞ 国 Ù³ ÞÝ Ù£ ¡á 国 Ïê Ïê 国 园 ï£ ÞÌ üÞ üÞ ÙÍ ÙÍ Ïê Ïê 园 ÙÍ êÖ 触 ÙÍ 国 园 ÍØ ÙÍ ÙÍ í» óã ªé üÞ ÙÍ ï£ 园 ÙÍ üÞ 国 üÞ 国 ÞÌ 国 üÞ 国 ÎÄ Ú¶ ÙÍ üÞ 国 Þç í» ÙÍ ËÍ Ï¡ ø£ Ú¶ ÙÍ ªé üÞ 国 êÖ ÙÍ ÙÍ ï£ 园 Ù³ Óö Ù³ 国 ÞÌ 国 üÞ 国 üÞ 国 Ï¡ ÙÍ Ú¶ ÞÌ 国 ÞÌ 国 ø£ «ê üÞ 国 ªé 园 ï£ 国 üÞ 国 ï£ 园 ìí ÙÍ 図 ÙÍ üÞ 国 êÖ üÞ 国 ÙÍ ÙÍ ÞÌ 国 国 国 üÞ 国 ÙÍ öµ Ú¶ ÙÍ Óö ªé ï£ 园 Ïê Ïê üÞ 国 国 ÙÍ ÞÌ 国 ÞÌ ÞÌ ï£ 园 ï£ 国 国 ÙÍ Ï¡ ÙÍ üÞ 国 园 ï£ 国 r «ê ÙÍ 図 国 ªé üÞ 国 ù½ Ú¶ ÙÍ öµ 园 ÙÍ Ï¡ üÞ 国 ÙÍ Ïê Ïê ÞÌ 国 ÙÍ Ï¡ 国 êÖ Óö 舗 Ï¡ 歹¡¢ Ú¶ ÙÍ Óö ÙÍ ªé 図 öµ ÙÍ 阳 Óö ¡á üÞ 国 国 Ïê Ïê 国 Ïê Ïê ï£ 园 üÞ 国 园 ï£ ªê 国 üÞ 国 Ï¡ ªé Ù³ ù¦ ÏÐ Ïê Ïê d \ öµ ÙÍ 阳 üÞ 国 üÞ 国 ÙÍ üÞ 国 ÙÍ 旧 ìí 吕 ÞÌ Ò½ ³Ö ÙÍ 国 国 ù¦ ªé Ïê Ïê 国 üÞ 国 ÙÍ üÞ üÞ Íë ÞÉ üÞ üÞ ÙÍ ÙÍ 国 与 国 侧 ÙÍ ËÁ üÞ 国 国 ÙÍ Ò´ êÅ ìí 国 画 図 ªé üÞ 国 Óö ÙÍ ìí ìí üÞ 国 触 ÙÍ 飪 ÙÍ ï£ 园 ù½ ÙÍ ÞÌ 国 国 ÞÀ üÞ 国 Ï¡ 図 歹 õó í» ÙÍ 図 ªê ËÍ ËÍ 园 Ï¡ 园 ÖØ ÙÍ Ï