aa:T490,

6.25 \times 10^{18}

72:["$","span","code-1",{"className":"SmxAaG_mathInline","data-math":"inline","tabIndex":"$undefined","dangerouslySetInnerHTML":{"__html":"$aa"}}] 73:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":"Define potential difference and 1 volt."}]]}] 74:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":["Work done per unit charge, ",["$","span","code-0",{"className":"SmxAaG_mathInline","data-math":"inline","tabIndex":"$undefined","dangerouslySetInnerHTML":{"__html":"

V = W/Q

"}}],"; 1 V = ",["$","strong","strong-0",{"children":"1 J/C"}],"."]}]]}] 75:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":"How are an ammeter and a voltmeter connected?"}]]}] 76:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":["Ammeter ",["$","strong","strong-0",{"children":"in series"}]," (low resistance); voltmeter ",["$","strong","strong-1",{"children":"in parallel"}]," (high resistance)."]}]]}] 77:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":"Symbol for a cell: which plate is positive?"}]]}] 78:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":["The ",["$","strong","strong-0",{"children":"longer, thinner"}]," line is +; the shorter, thicker line is −."]}]]}] 79:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":"State Ohm’s law."}]]}] 7a:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":["V across a metallic wire is proportional to I through it, ",["$","strong","strong-0",{"children":"provided the temperature remains the same"}],": ",["$","span","code-0",{"className":"SmxAaG_mathInline","data-math":"inline","tabIndex":"$undefined","dangerouslySetInnerHTML":{"__html":"

V = IR

"}}],"."]}]]}] 7b:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":"What does the slope of a V–I graph give?"}]]}] 7c:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":["The ",["$","strong","strong-0",{"children":"resistance"}]," (V on the y-axis); steeper line = larger R."]}]]}] 7d:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":"1 ohm"}]]}] 7e:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":"Resistance of a conductor through which 1 A flows when 1 V is applied."}]]}] 7f:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":"What is a rheostat used for?"}]]}] 80:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":["To ",["$","strong","strong-0",{"children":"change the current"}]," in a circuit without changing the source."]}]]}] 81:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":"Formula linking R, ρ, l and A"}]]}] ab:T6ad,

R = \rho \dfrac{l}{A}

82:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":["$","span","code-0",{"className":"SmxAaG_mathInline","data-math":"inline","tabIndex":"$undefined","dangerouslySetInnerHTML":{"__html":"$ab"}}]}]]}] 83:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":"SI unit of resistivity; does it depend on the length of the wire?"}]]}] 84:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":[["$","strong","strong-0",{"children":"Ω m"}],"; no — it depends only on the material and temperature."]}]]}] 85:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":"A wire is stretched to twice its length. New resistance?"}]]}] 86:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":[["$","strong","strong-0",{"children":"4R"}]," (length ×2, area ÷2)."]}]]}] 87:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":"Why is nichrome used in heating elements?"}]]}] 88:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":"High resistivity and does not oxidise readily at high temperature."}]]}] 89:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":"Why are copper and aluminium used for wires?"}]]}] 8a:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":["Very ",["$","strong","strong-0",{"children":"low resistivity"}],": little energy is wasted."]}]]}] 8b:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":"Series: what is common, what adds, and R_s?"}]]}] ac:Te63,

R_s = R_1 + R_2 + R_3

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\frac{1}{R_p} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3}

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R_p = \dfrac{R_1 R_2}{R_1 + R_2}

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H = I^2Rt

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I^2R

"}}],")."]}]]}] 9f:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":"Three formulas for electric power"}]]}] b0:Tccd,

P = VI = I^2R = \dfrac{V^2}{R}

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3.6 \times 10^6

a2:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":[["$","span","code-0",{"className":"SmxAaG_mathInline","data-math":"inline","tabIndex":"$undefined","dangerouslySetInnerHTML":{"__html":"$b1"}}]," J"]}]]}] a3:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":"Is kWh a unit of power?"}]]}] a4:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":["No — it is a unit of ",["$","strong","strong-0",{"children":"energy"}],"."]}]]}] a5:["$","div",null,{"className":"SmxAaG_md","lang":"$undefined","children":[["$","p","p-0",{"children":"Resistance of a 100 W, 220 V bulb"}]]}] b2:T6b1,

R = V^2/P = 484\ \Omega

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I^2R

"}}],"."]}]]}]

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